radiator filling

Add coolant to the reservoir bottle, check the line depending whether the vehicle is hot or cold and add to the line.I always do this with engine cold, then start the engine run it until it reaches normal temperature, check level on reservoir and repeat the procedure as needed. As the engine rises in temperature, the system will absorb the coolant and there will be room in the reservoir to add the full amount needed.

the radiator did not take the reservoir coolant once car reached certain temperature; car still blowing hot air thru ac; low coolant light is still on

Your AC has nothing to do with the engine cooling system. You are getting hot air through your AC/heating vents because some part of the AC system is in need of attention. You mentioned the light isn't on to indicate AC is on so it could be any component of that system. Might want to make sure your AC compressor clutch is engaging which will make a clicking noise that will come from the bottom of the serpentine belt closer to the firewall. The AC Compressor pulley is connected to the serpentine belt which is constantly turning. The compressor clutch allows the spinning pulley to engage and disengage the compressor. If it ran constantly the pressure created by the compressor would increase without interruption causing damage to the AC system. If you don't hear the clicking the clutch is bad or clutch relay is bad. If you do hear the click then your AC may need to be recharged with coolant. This system is closed so the only reason that it would lose refrigerant on its own would be from a leak somewhere. You can find refrigerant with stopleak additives for the same price as regular refrigerant so you may as well get that. Two 12oz cans should be plenty. You will need to buy a hose if the cans you buy don't include one. I bought a charging hose for $12 and the refridgerant was like $7/can. Follow instructions online or on the can and you should feel a noticeable difference in the temperature. Your not out of the woods yet though... Enjoy your cool air while its flowing because if the leak is coming from something more than rubber seals or the like, it could be coming from one of the more expensive components of the AC system like the compressor, accumulator or condenser. Honestly if that were the case with mine I would have settled for rolling the windows down!lol