How to activate a relay with a 433mhz RF board?

I have a raspberry pi set up which already activates a relay via GPIO. Right now I want to activate a relay wirelessly to turn a light off and on. What would I have to do to use a 433mhz board(transmitter at the pi, receiver at the relay) to turn the light on and off? Or if there is an easier to do this then I'd much rather hear about that.

Thank you.

Buy a transmitter board and a receiver board ? Use the existing relay to "press" the button on the transmitter.