Controlling a stepper motor and getting data from an RC receiver (presumably you do have a receiver?) are two different tasks and you should start with two separate programs for them. When you can get both of them to work separately it will be time to combine them.
Is your RC transmitter / receiver the common sort of thing that is used to control servos in, for example, a model airplane? If so, your Arduino program will have to measure the width of each pulse and convert that to a suitable number.
If you have the option I think it would be much easier to build a wireless control system using a pair of nRF24L01+ transceivers. Have a look at this Simple nRF24L01+ Tutorial
For controlling the stepper motors these links may help
Stepper Motor Basics
Simple Stepper Code