The picking pattern for the intro and first verse goes like this:

e |--------------------------------------------|
B |--------------------------------------------|
G |--------------x-------------------x---------|
D |-------------------x-------------------x----|
A |---------x-------------------x--------------|
E |----x-------------------x-------------------|

Intro/verse
Use your index finger to get the notes on the G string, and bar the rest with your middle.

e |----x---------x---------x---------x---------|
B |----x---------x---------x---------x---------|
G |----8---------7---------5---------5---------|
D |----(b9)--------7---------5---------5---------|
A |----(b9)--------7---------5---------5---------|
E |----(b9)--------7---------5---------5---------|

Chorus (I've got a long black river...)
Stay on the last chord (G Maj) until the chorus ends.

e |----x---------x---------x---------x-----x---------x---------|
B |----x---------x---------x---------x-----x---------x---------|
G |----1---------3---------5---------8-----7---------5---------|
D |----2---------4---------5---------(b9)----7---------5---------|
A |----2---------4---------5---------(b9)----7---------5---------|
E |----2---------4---------5---------(b9)----7---------5---------|