I found a baby bird that has fallen from its nest?

It has feathers and its eyes are open. I think it is injured in either its leg or wing. He is also shaking. I found him today and am now keeping him in a shoebox with towels a mushed banana. I have no clue what to feed him or what to do. I am very scared, I've never cared for a baby bird before and have no clue what i'm doing. If anybody could help I'd very much appreciate it! Or does anybody have a phone number for any rehabilitaion centers in orange county? Thank you soo much for your help!