You should only do this on your own if you are experienced in electrical connections. You’ll need a double-pole 50-amp breaker box with a vacant location. If you don’t have one, you’ll need to install one. Once you have that, you can purchase a 50-amp breaker, your 50-amp wire, and a 50-amp box from a local hardware store. Connect your 50-amp wire to the breaker, trench to bury the wire (if needed), then connect your wire to the box where you want your RV to have access to the power supply.