The coolant can be drained from the radiator using a plastic tap on the drivers side, inboard on the radiator. Use a hex wrench to carefully loosen it and remove it. Don't break it off. There will still be some coolant in the engine block though. There is at least one drain plug on the block also.

Use coolant safe for all metals. Volvo coolant of course if fine, but there are others if you don't have a dealer around. I would replace the thermostat if you haven't done so lately. Its about 12 bucks and is easy to do, located where top rad hose enters the engine. Check the hoses too, now is good time to change those. Top one is easy, bottom one is harder to do, but not impossible.