Okay, so this is my first tab, hope I'm doin' it right!

Tuning: Standard

Intro + Whenever they sing the "I'm gonna sing this song with all of my friends" part
E------------------------------------------------------|
B--- 6 6 6 6 6 6 6 5 5 -------------- 10 10 --- 7 ---- |
G------------------------- 7 5 --- 5 ----- 10 ---  10--| x however many
D----------------------------- 7 8 --------------------|
A------------------------------------------------------|
E------------------------------------------------------|

And, the "We'll aim for the stars, we'll aim for your heart" part

E------------------------------------------------------|
B- 13 13 10 11 13---13 13 10 11 13--11 10 8 6----------|
G------------------------------------------------------| x2
D------------------------------------------------------|
A------------------------------------------------------|
E------------------------------------------------------|

and the very end (the part that's kind of like the "we'll aim for the stars" part, but lower
E------------------------------------------------------|
B-10 10 6 8 10 8--------10 10 6 8 6--------------------|
G------------------------------------------------------|
D------------------------------------------------------|
A------------------------------------------------------|
E------------------------------------------------------|

So, I hope this helped, and is alright! It's a pretty easy song, and it's fun to play, 
good luck!