Setting up your transmitter so it will serve you as a simulator joystick is quite straightforward.
You need a cable to connect your transmitter to your computer. You can either create your own cable or buy one. The cable's transmitter-end varies according to the type of the transmitter. Some transmitters (e.g. JR, Spektrum) require a very cheap cable while other transmitters require a more elaborate one.
In the Cables section you will exact instructions how to create and what to buy.
Download SmartPropoPlus installation package.
Everything is in the Download section.
Follow the instructions carefully. In most cases you will be simulating within 5 minutes from now.
According to the simulator, select joystick vJoy Device as you joystick. In many cases you will have to make some final adjustments such as axis assignments, axis inversion and calibration.