This song is pretty simple:  G C Em D for everything except the bridge, which is G G/B C; A A D (half time).  

Capo 1

G C Em D x2

          G           C        Em             D
There's a girl in the backyard banging on her drum
   G         C         Em              D
Sitting in a junk pile laughing at the sun
         G     C          Em         D
Singing "Ah ha ha, I just wanna be a rockstar"

G C Em D

          G          C        Em             D
There's a boy in the backseat singing to the song
    G          C      Em               D
Playing on the radio, knowing he's the one
         G     C          Em         D
Singing "ah ha ha, I just wanna be a rockstar"

G C Em D

         G     C         Em           D
Singing "ah ha ha, I was born to be a rockstar"

G C Em D x2

          G           C        Em             D
There's a girl in the tree top looking at the stars
   G          C         Em             D
Waiting for a touchdown coming in from Mars
        G C            Em  D
Thinking   "is there anybody out there?"

G C Em D

          G            C      Em             D
There's a boy thinking of her playing his guitar
    G              C     Em            D
Searching for the answer buried in his heart
         G     C             Em      D
Thinking "ah ha ha, is there anybody out there?"

G C Em D

         G     C            Em      D
Singing "ah ha ha, is there anybody out there?"

G G/B C
                             A A         D
If there's a meaning can you show me a sign
                             G G/B        C
The more I look it just gets harder to find
                            A A         D
The world is spinning and I wanna know why

G C Em D x2

          G           C      Em             D
And we're all getting older wishing we were young
    G          C         Em             D
Hanging on the memory of what we would become
         G     C         Em           D
Singing "ah ha ha, I was born to be a rockstar"
         G     C          Em         D
Singing "ah ha ha, I just wanna be a rockstar"
         G     C         Em           D
Singing "ah ha ha, I was born to be a rockstar"

G G/B C
                             A A         D
If there's a meaning can you show me a sign
                             G G/B        C
The more I look it just gets harder to find
                            A A        D
The world is spinning and I wanna know why

G G/B C
                        A A         D
And maybe we will never figure it out
                            G G/B         C
I got a feeling that's what life's all about
                         A A         D
I'm learning anything is possible now

G C Em D x2

G                     C           Em D
Take a ticket and get off the line       x8

         G     C         Em           D
Singing "ah ha ha, I was born to be a rockstar"

G C Em D

         G     C         Em           D
Singing "ah ha ha, I was born to be a rockstar"

G C Em D

         G     C          Em         D
Singing "ah ha ha, I just wanna be a rockstar"

G C Em D

         G     C         Em           D
Singing "ah ha ha, I was born to be a rockstar"

G C Em D x3

G C