This is a legendary song called heart and soul. A very popular piano song.
G|-----------|-----------|-----------|-----------|
D|-2---------|-----------|-----------|-----------|
A|-----------|-3---------|-0---------|-2---------|
E|-----------|-----------|-----------|-----------|
Or you can play it in chords, like this:
G|-----------|-----------|-----------|-----------|
D|-2---------|-----------|-----------|-----------|
A|-3---------|-3---------|-0---------|-2---------|
E|-----------|-5---------|-1---------|-3---------|
The bass plays that for the whole song. If not, ask a professional. I'm not one!!