Donna, no gems of knowledge but just to say that it happened to the first chicken I got last year. As a complete novice I hadn't got a clue.
There are some good u-tube videos if you aren't certain what to do.
I used prep h cream and also some honey.
The first couple of days I was putting the prolapse back in about 4 times a day and after that I needed to do it just once or twice until it eventually stayed in. She was never able to lay an egg though.