This is the main riff, it is played through the whole song: just repeat it.

G |: ----------------|
D |: ----------------|
A |: 3-------6---1---|
E |: ----4-----------|

    Or you can play it like this:

G |: ----------------|
D |: ----------------|
A |: 3-------6---5---|
E |: ----4-----------|

    And really that's it. Please tell me if it needs to be corrected.