Although labelled as an "intro", this riff carries on at different parts of the song. 
played on keyboard, you might as well know it on guitar too.

Guitar riff, check song for timing of riff:

E|---3-----1-3-6-----------1---------------------------|
B|---------------3-----1-3--------------3--------------|
G|----------------------------3-----2-3----0-----2-3---| *Repeat*
D|-----------------------------------------------------|
A|-----------------------------------------------------|
E|-----------------------------------------------------|

That's it. It just repeats over and over at different point in the song.

Enjoy!