I am new to chess and am confused on what to do with the following opening
[fen ""] 1. e4 e5 2. Nf3 Nf6 3. Nc3 Bb4
I have been playing
4. a3, but the Bishop then proceeds to take c3 so I end up with a doubled pawn.
If someone could offer some guidance or tell me what this opening is called so I can do some research, it would be very much appreciated.