I have seen the same tab for this song all over the interent, and it's not right.
So here is how you play Three Marlenas the RIGHT WAY.  It can be played with or without a capo
but it's a lot easier to play it with a capo, so CAPO the 1st FRET.

The Chords are D, A, G   and then  G, A, D

Listen to the song for the stumming pattern, this is reapeated throughout the whole song..