How do I setup chess positions and play against the computer.

Is there a way for me to setup a chess position and then have a computer play against me. Example, setup two bishops + king vs King. I want to practice different scenerios against the computer, so that I build my skills.

Yes, please take a look at the Computer Workout which will give you numerous positions that you can train and practice with the Computer.

http://www.chess.com/computer-workout/

It appears they are preestablished positions, when using the Computer Workout. What I am looking for is to create the position and then have the computer play against me, starting from that position. Is there anyway to do that on this site?

This would be a good thing to have. It seems that the computer workout has mainly endgame positions but practicing different openings would be good and of course just being able to make your own starting position would be the best.

any number of chess programs will have a position editor. The one I use does;

http://www.sigmachess.com/

but that's only for a mac.

you an do it on chessmaster

Why can we do this (setup the exact postion we want, and then play against the computer)on the iPhone version of chess.com, but not on this site?? This makes no sense . . .