If you really overheated the engine, the smart move is to replace the head gasket and have the head checked at a "good" machine shop. Depending on how many miles on the engine, check all the valves in the head too. Maybe do the the timing belt and water pump while everything is apart anyways.

A little overheated.......just cure the problem and fill it up with coolant.

A lot overheated.....may require up to a complete rebuild. New rings , bearings, gaskets and a planed head. If you include the labour, it may be better to buy a used engine in good condition.

overheated as in it's destroyed, or overheating as in the motor is good, but over heats.

Check for air in the radiator, make sure the cap it pressurized, the coolant is the right mixture, thermostat is working good,etc.

You let it cool off. Then check the amount of anti-freeze and test it for the proper ratio.