Hi, I haven't performed in festivals, but from what I've seen from live performances, the pianist enters the stage and bows to acknowlege the audience. After the first piece, they stand and bow again to acknowledge the applause. The same is repeated for the second piece.
They normally stand to the front of the stage a little way away from the piano stool. Some stages have a mark that you stand on, so look out for that too.
If you have to introduce your pieces speak loudly and clearly enough for all to hear (depending on the size of the room/hall), giving the title of the piece and the composer.
Hope this is of some help

Enjoy the festival. Which pieces are you playing?