How do you stop a program thats running on the board?
Turn the power off.
Also, is there a listing of the error messages in the IDE?
The messages are quite obvious. Why would they need to be listed anywhere.
Well, they are after you’ve seen them a few hundred times. In your case, the compiler is telling you that you are referencing a name, IP, that is not in scope where you reference it.
We can’t tell what changes you have made to the sketch you are trying to compile (even inadvertently), so posting where you got the sketch, rather than the sketch, is a waste of time.
The thing Just plugs in on top of the other board. Does it not?
It does, but all those pins are not just for alignment purposes.