Greetings night owl.
Get yourself a flush and fill kit, and a bottle of peak superflush (or whatever the name is on the bottle today!) Get the flush chemical that stays in for about 30 minutes not the drive around with it for a week brand. CONFIRM your car has no leaks and doent overheat anymore. If it does have problems, finish your flush and then make repairs.
The flush kit adds a hose adapter to your heater hose. It is important to do a REVERSE flush especially to get crud out of the heater core. Use the picture on the directions to guide you to the right hose. I use a short piece of hose to put the adapter in temporarily and then reconnect the full hose later. After the flush is done pull the lower rad hose to drain most of the water out. NOTE! This is a great time to replace any old hoses. Reinstall lower hose and fill with FULL STRENGTH coolant. You know the capacity so you know how much to use to make a 50/50 mix. You will have to top up the system a number of times before it will be totally full. Keep an eye on it. Add 50/50 mix to the reservoir.
That should keep you busy for a while.
Dont do ANY of this until you are sure your car has thawed. Antifreeze doesnt thaw ice. It only keeps it from happening. If any of your cooling system is frozen you wont be able to do this job correctly.