Hi, I also believe that you should get a radio with minimum 6 channel if you want to use all your NAZA-M capabilities. Beside the four basic functions (Ail - Rud - Elev - Throttle) a 3 way switch is required for your flights mode (GPS - ATTITUDE + Failsafe or Manual). Of course, you can fly with a 2 way switch but that will require that you connect and change its' function once in a while. Other functions such as Intelligent Orientation Control, AKA IOS, requires another 2 way switch and gimbal control requires one as well.
When it comes to the DJI assistant, it is normal to get an error message if your receiver is not binded to your Tx. The first step is to bind both the Tx and Rx which is different from companies to companies. I believe that in your case you need to connect the jumper connector which jumps pin 1 and 3 prior to power up. Then you press the training switch and THEN your turn on your tX. When you see binding on the screen (if you have one) release the button. The Rx light should go from flashing to solid. When this is done turn everything off, remove the binding jumper in the receiver and power up again. If you get the solid light again, it worked!
Hoping it helps.