You really need to consult the relevant manual for the car-what car is it? Presumeably you think there may be airlocks in the system, and want to drain/flush/refill to see if it helps.
Here's a few general pointers: Depending on the car, the refill and bleed method differs, and can often be quite complicated.
Some cars have small bleed valves in the system (My XUD engine, for example, has two bleed valves: one in the thermostat housing and one in the rad top) and some cars require you to rig up a high level header tank (usually home made from a plastic pop bottle) See if you can spot any small valves in the cooling system (but don't confuse them with aircon access points) .
Others can only be really succsessfully bled by removing aa heater hose and running the engine until the air is expelled and water comes out (small Fiats of ye olde days)
When you've drained the system, flush it both ways with a hosepipe and also use a chemical cleaner- if you have blockages or silting this will help lots. Some cars (205 GTi's for example) were very prone to rad silting and consequent overheating, and a regular flush/clean made a world of difference.
Once you have the system clean and refilled/bled, then you can assess the problem, if any, more accurately.