Put the air lock on and sit back. If you want to be scientific you can use your hydrometer and take a reading. This batch came in at 1.100 SG (specific gravity) which is a potential alcohol content of 22% when it is finished fermenting. I find it hard to believe it will finish at 22%, however this batch should be very dry. I may add more apples in the first racking depending on the first tasting.