I want to make sure I understand. Whatever key the piano music is written in, you raise it a step higher?

If you are playing a Bb instrument, yes. Well, you raise it a tone higher. So if written note is a C, you read a D, if a D, an E, if an E, an F# and so on...There's another method you can try if you know the sequence of sharps and flats. It turns out that for transposing up a tone, you either gain two sharps or lose two flats. So if the piano has three flats(Eb major), you play with one flat (F major); if the piano has two flats, you play with none; if it has one flat, you play with one sharp; and if the piano is playing with no sharps or flats (in C), you need to play with two sharps (in D).