If the plane has only one set of controls, push, pull, carry, or drag the pilot out of the pilot's seat. Take your place at the controls. Depress the button to talk, release it to listen. If you get no response, try again on the emergency channel-tune the radio to 121.5.
All radios are different, but tuning is a standard procedure.
The person on the other end should be able to talk you through the proper landing procedures. Following their instructions carefully. If you cannot reach someone to talk you through the landing process, you will have to do it alone. Get your bearings and identify the instruments. Unless you have just taken off or are about to land, it should be flying relatively straight.