You just need to find a ESC (Electronic Speed Controller) that meets your needs for voltage and current. With a standard 775 motor, you're looking for a "brushed ESC".

Look for what voltage it is rated for. Many are rated to 8.4V, some up to 11V and some beyond. If you want to power the motor from a 12V battery, look for something rated for 16V or higher. Most 775 motors aren't going to draw huge amounts of current, but check the Amps (A) rating of the ESC exceeds the maximum current of the motor.

The ESC will easily plug into any standard radio receiver and you will be able to control the speed from your transmitter.

This is not a recommendation, but an example: https://hobbyking.com/en_us/hobbywin...ontroller.html

Suggest you go to your nearest hobby shop and they should be able to help you.