The open 3rd string is an A note
Play this B note with the second finger of your left hand just behind the second fret of the 3rd string
Play this C note with the third finger of your left hand just behind the third fret of the 3rd string
The following progressions use quarter notes and half notes.
The name of the note the bass player plays is not necessarily the same as the name of the chord, e.g.: in bars 2, 3 and 4 of the above example the bass plays a different note than the chord name.
As a general rule: