- Start the external keyboard, then start MusicMaker
- Select an Asio Driver, ASIO4All or WASAPI in the Program Settings
- Make sure that your external keyboard is the selected input device in the Program Settings
- Select an instrument for the track
- Arm the track for MIDI recording
- Don't try to record using the keyboard at the bottom of an instrument
- Make sure the yellow bar at the top starts where you want to start recording and, preferably, ends beyond the length that you intend to record
- Press on record and play your external keyboard
Do you see the keys move on the on-screen keyboard (bottom window) when you press on a key on your external keyboard?
Without seeing your setup, it's hard to help more.