Q: I can't seem to connect my MIDI keyboard to Garageband.

Hi there, I have a question. When I connect my synth keyboard the screen will come up from garageband that says it detects it, but when I play on the synth nothing comes through the master volume level (which is located at the bottom of the screen next to the metronome button), so therefore nothing I play on the keyboard comes through, meaning it wont record anything. I've tried everything, but I just cant seem to figure out how to get it playing. Do you have anything suggestions? Thanks!