Have a look at
http://www.guitarforbeginners.com/rocky/ ... I did a quick movie of the part he (sort of) plays.
It's in the key of E, but capoed up on the second fret, played in dropped D. The way I did it was to hold down and frail away at a little D triad and work the line around it, picking with my thumb. It then goes to a G and then an A. After I finished I noticed the tab you posted. It's pretty much exactly that except I didn't make the Em so noticeable, and I played the A chord as a triad, not a power chord at the 7th fret (well, 9th fret counting the capo).
I hope you can see how it's done. As always, it's the flow, the feel, the vibe of it that is the important ingredient.