In situations where you only have one bishop left the general rule of thumb, usually atributed to Capablanca, is to place your pawn on the opposite colour to that bishop. This way the pawns won't obstruct the bishop while helping to control the squares unavailable to it.
Of course there are always exceptions to this rule but they probably don't matter too much for you right now.
So often in my games, I find myself placing pawns on the same-coloured squares as one (or both) of my bishops, sometimes trapping them inside. Are there any situations where it is useful to have your pawns and bishop(s) on the same coloured squares? Dumbed down please, I'm only a beginner.