how do I record my Casio keyboard
I have an iMac running 10.9.5 with Garageband 10.0.3. I'm completely new to GB. I connected a Casio keyboard using the USB port, and GB says 1 midi input is detected. GB will not record via the USB connection; it records only through the built-in mic. The only options for input in GB are "system setting" and "built-in mic". I've tried both of those. In System Preferences/Sound there is just "built-in mic" and no other options. How do I disable the built-in mic and record via the USB connection? (I checked the Casio instructions, and they mention something about downloading a data manager driver to the computer; but when I went to the web site link I could not find anything having to do with a data manager driver.)
GarageBand 10, OS X Mavericks (10.9.5)