This song is super easy. There is only two main chords the whole song, I added a few in 
to make it a little less boring.
They are the chords in brackets so you can play them if you want!
 

     D
Hey, boy you never had much game
                Bm
Thought I needed to upgrade

So I went and walked away way way
 D
Now, I see you've been hanging out
                  Bm
With that other girl in town

Looking like a pair of clowns clowns clowns

  D
Remember all the things that you and I did first?

And now you're doing them with her
Bm
Remember all the things that you and I did first?

You got me, got me like this
 D
And now you're taking her to every restaurant

And everywhere we went, come on!
 Bm
And now you're taking her to every restaurant

You got me, got me like this

D
Boy you can say anything you wanna

I don't give a shh, no one else can have ya
Bm
I want you back
(G)
I want you back
 (A)              (D)
Wa-want you, want you back
D
I broke it off thinking you'd be cryin'

Now I feel like shh looking at you flyin'
Bm
I want you back

I want you back
                D
Wa-want you, want you back 

 It's important that you satisfy the clearances if you want to play it right. 
You should play every chord on it's right place. 

Capo 2

Intro: C G Am G 

C
Hey, boy you never had much game
           G Am
Thought I needed to upgrade
                      G
So I went and walked away way way
C
Now, I see you've been hanging out
           G    Am
With that other girl in town
                          G
Looking like a pair of clowns clowns clowns

BRIDGE:
C
Remember all the things that you and I did first?
                     G
And now you're doing them with her
Am
Remember all the things that you and I did first?
                    G
You got me, got me like this
C
And now you're taking her to every restaurant
                G
And everywhere we went, come on!
Am
And now you're taking her to every restaurant
                    G
You got me, got me like this

CHORUS:
C
Boy you can say anything you want 
                        G
I don't give a shh, no one else can have ya
Am
I want you back I want you back
                   G
Wa-want you, want you back
C
I broke it off thinking you'd be cryin'
                        G
Now I feel like shh looking at you flyin'
Am                    
I want you back I want you back
                   G
Wa-want you, want you back

C 
Please, this ain't even jealousy
            G    Am
She ain't got a thing on me
                             G
Tryin' to rock them ugly jeans jeans jeans
C
You clearly didn't think this through
             G     Am
If what I've been told is true 
                            G
You'll be crawling back like boo hoo hoo

BRIDGE:
C
Remember all the things that you and I did first?
                     G
And now you're doing them with her
Am
Remember all the things that you and I did first?
                    G
You got me, got me like this
C
And now you're taking her to every restaurant
                G
And everywhere we went, come on!
Am
And now you're taking her to every restaurant
                    G
You got me, got me like this

CHORUS:
C
Boy you can say anything you want 
                        G
I don't give a shh, no one else can have ya
Am
I want you back I want you back
                   G
Wa-want you, want you back
C
I broke it off thinking you'd be cryin'
                        G
Now I feel like shh looking at you flyin'
Am                    
I want you back I want you back
                   G
Wa-want you, want you back

C               G     Am
Ohhh, I thought you'd still be mine 
                          G
When I kissed you goodbye uh oh uh oh
C             G     Am
Ohhh, and you might be with her 
                          G
But I still had you first uh oh uh oh

BRIDGE:
C
Remember all the things that you and I did first?
                     G
And now you're doing them with her
Am
Remember all the things that you and I did first?
                    G
You got me, got me like this

CHORUS:
C
Boy you can say anything you want 
                        G
I don't give a shh, no one else can have ya
Am
I want you back I want you back
                   G
Wa-want you, want you back
C
I broke it off thinking you'd be cryin'
                        G
Now I feel like shh looking at you flyin'
Am                    
I want you back I want you back
                   G
Wa-want you, want you back 

C   G Am
Ohhh, I want you back
I want you back        G

Wa-want you, want you back

C   G Am
Ohhh, I want you back
I want you back 
                  G
Wa-want you, want you back 

 Intro; G D Am C x2

G                   D
Hey, boy you never had much game
             Am
 So I needed to upgrade
               C
So I went and walked away-way-way
G                   D
Now I seen you been hanging out
                 Am
With that other girl in town
                  C
Looking like a pair of clowns-clowns-clowns

G
Remember all the things that you and I did first
D
And now you're doing them with her
Am
Remember all the things that you and I did first
C
You got me got me like this
G
And now you're taking her to every restaurant
D
And everywhere we went, come on!
Am
And now you're taking her to every restaurant
C
You got me got me like this

G
Boy you can say anything you wanna
D
I don't give a sh, no one else can have you
Am
I want you back, I want you back
C
Want want you, want you back
G
I broke it off thinking you'd be crying
D
Now I feel like sh looking at you flying
Am
I want you back, I want you back
C
Want want you, want you back

G                  D
Please, this ain't even jealousy
                Am
She ain't got a thing on me
                      C
Tryna rock them ugly jeans-jeans-jeans
G                      D
You clearly didn't think this through
                    Am
 If what I've been told is true
                     C
 You'll be crawling back like boo-hoo-hoo

 G
Remember all the things that you and I did first
D
And now you're doing them with her
Am
Remember all the things that you and I did first
C
You got me got me like this
G
And now you're taking her to every restaurant
D
And everywhere we went, come on!
Am
And now you're taking her to every restaurant
C
You got me got me like this

G
Boy you can say anything you wanna
D
I don't give a sh, no one else can have you
Am
I want you back, I want you back
C
Want want you, want you back
G
I broke it off thinking you'd be crying
D
Now I feel like sh looking at you flying
Am
I want you back, I want you back
C
Want want you, want you back
 G       D                 Am
Oooh, oooh, I thought you'd still be mine
              C
 When I kissed you goodbye uh-oh uh-oh
G                       Am
 Oooh, oooh, and you might be with her
              C
But I still had you first uh-oh uh-oh
G
Remember all the things that you and I did first
D
And now you're doing them with her
Am
Remember all the things that you and I did first
C
You got me got me like this
G
And now you're taking her to every restaurant
D
And everywhere we went, come on!
Am
And now you're taking her to every restaurant
C
You got me got me like this

G
Boy you can say anything you wanna
D
I don't give a sh, no one else can have you
Am
I want you back, I want you back
C
Want want you, want you back
G
I broke it off thinking you'd be crying
D
Now I feel like sh looking at you flying
Am
I want you back, I want you back
C
Want want you, want you back