I'll tell you if you want to add points: two barrels of 4L are enough. If there is a drain valve under the water tank, just send it away. If not, remove the drain pipe and drain it (be careful to push the temperature adjusting lever on the air conditioning control panel to the warm air position to drain the antifreeze in the warm air water tank). When there is no water flowing out, put it back in place, add new antifreeze, and start the engine (without cover) after filling it up.
I hope it helps you.