1st of all use some good cooling system flush to clean the cooling system. Check the condition of radiator, radiator cap, & cooling system pipes etc. and replace with new if required, then pour good coolant/antifreeze in cooling system.
But its not the end, the rust, corrosion, salts built up for more than 10 years will not that easy to be cleaned and it will gradually cleaned and during this cleaning process u may face failure of different old components like radiator, pipes, heating coil, thermo stat housing, water pump, Intake manifold or any other component associated with cooling/heating system. So keep it under thorough observation, and in case of leaks and cracks etc,. have tem fixed accordingly.