For your keyboard outs, run the left and right in the two channels and record in stereo. Most of the sounds from a keyboard are stereo.
Now, for the MIDI, and you're gonna have to do some research, But open all (it is the easiest for now) channels (1-16, should be some all send or something setting), set it to record, make sure your MIDI In is connected to your MIDI Out and vice verse between the interface and the keyboard (it is actually logical, what is going out from one is going in from the other). If you don't see a signal, you will need to read the instructions on your keyboard on how to open that up and to send and receive. Record a few measures until you get MIDI data flowing.
Once you have that working, now you work on getting the recorded MIDI data back to your keyboard. You will have to once again look at your keyboards instructions to set the keyboard up to receive MIDI data (There are program changes and the like, but you can work on that later) When you know the data is arriving back to your keyboard (headphones or speakers), then you know data is be sent and received. When that happens, you record the voices from the keyboard just as if it were being played live, cause it is, just not by human hands. There will be a slight delay, so you will have to line it back up, but you should be able to do it in one nudge or two nudges to the left. (You could set a signal on a measure marker for alignment purposes).
Lots to deal with, but if you get it working, it really adds power to your recording.