Download and install the latest "legacy keyboard" driver from M-Audio's website at m-audio.com. The Radium will not work with the included drivers on the most recent versions of Windows and OS X.
Connect the Radium to an unused USB port on your computer. The Radium can receive power from the USB port. If your ports cannot power peripheral devices, use a 9V DC power adapter to plug the unit into an outlet. A generic adapter will work without problems.
Turn the Radium on. With the correct driver installed, your system will recognize the device automatically.
Open the software sequencer or other MIDI editing application of your choice. Any application that can receive MIDI data from an external device should work with the Radium.
Open the application's audio/MIDI preferences dialog, usually accessed under the "File" menu in Windows or under the application name menu in OS X.
Set the Radium as the MIDI input device for the application. In some cases, the application will use any attached devices automatically, but some require the user to choose. It will appear as "USB keyboard," "MAudio keys" or similar in the list of devices.
Instantiate a software MIDI instrument on a new track in your application and play some notes on the Radium. You should hear the software instrument play back the notes you press. Consult your sequencer's documentation for details on establishing continuous controller settings, MIDI channel setting and other information related to using an external MIDI device.
Make sure the Radium is switched off and plug the unit into an outlet using a 9V DC adapter. The adapter is sold separately.
Turn the hardware MIDI instrument off before wiring between the two components.
Connect the standard MIDI cable to the Radium's "MIDI Out" port, located on the back of the unit, and connect the other end to the "MIDI In" port on the MIDI instrument.
Connect the MIDI instrument to monitor speakers or headphones if it does not have built-in speakers.
Turn both devices on and make sure the MIDI instrument is receiving on MIDI channel one or omni. Consult the device's documentation for details.
Play some notes on the Radium. You will hear the MIDI instrument play back the notes you press.