youll have to tune your A string down so that its 7th fret matches your open G string. 

intro:
-------------------------------|
-7--7h9-9p7-7-7h9/12-----------|
-7--7---7---7-7----------------|
-------------------------------|

-------------------------------|
-7--7h9-9p7-7-9p7\5/7----------|
-7--7---7---7------------------|
-------------------------------|

verse:
-------------------------------|
-7--7h9-9p7-7h9p7h9------------|
-7--7---7---7------------------|
-------------------------------|
i was sittin on top of the world
i really had things in my hand

--------------------------------|
---6/12---12\8------------------|
-5------5-----------------------|
--------------------------------|
then something went wrong im not sure what

chorus:
----------------------------------|
-11---10-10-10--------------------|
-11---10-10-10--------------------|
----------------------------------|
i lost everything i had...
startin over from scratch


thats basicly everything, if you know the song youll have no problem putting it all together