How To Hook Up A MIDI Keyboard To Use With Mixcraft
A MIDI keyboard or controller allows you to use your computer like a synthesizer.

If You Have a MIDI Keyboard Already:
If you have a MIDI keyboard, you will need a USB MIDI interface to connect to your computer.  USB MIDI interfaces will cost anywhere from $30 to $200.  Install the drivers for the USB MIDI interface and then hook up the MIDI interface to your computer.  It's also possible that the computer's sound card already has a MIDI port and, thus, you would not need an extra USB MIDI interface.

Connect a MIDI cable in the MIDI-Out of your keyboard to the MIDI-In of the MIDI Interface and you'll be ready to record.

If You Don't Have A MIDI Keyboard:
Your best option is to purchase a USB MIDI keyboard controller.  You can purchase them from around $70 to $1000, depending on quality, number of octaves, size and performance.  Once you have the USB MIDI keyboard controller, simply a USB cable from the MIDI keyboard to the computer and you'll be ready to record.

Alternatively, you can use the built in Musical Typing Keyboard (MTK).

What MIDI Channel Should You Use?
Mixcraft does not care what MIDI channel you are playing on your keyboard and will record on any MIDI channel by default.