Right on, glad you're enjoying the lesson.
As for the bass, it is primarily playing what is known as a "walking bass line", which doesn't just stay on the root note of each chord, but moves through a series of notes to give the feeling of movement.
For example, under one meausre of the A chord, the bass will play on the beat with quarter notes, and play the notes: A, C#, E, and F#. Simply transpose this pattern down one string set and you'll find the notes to play under the E chord (E, F#, A, and B).
That should get you in the ballpark for a big chunk of the song. There are a few spots where the acoustic guitar plays a walk up or walk down, and the bass would simply play the same as the guitar in those spots.
Hope this gives you something to go on!
Keep rockin',
Mike
Keep rockin!
Mike Olekshy
GT Guitar Coach