Drip acclimation is putting the animal, with the water he came in, in a bucket. Then you can either set up a drip line from your tank, or pour a cup of water from the tank into the bucket every 15 minutes or so. When the time is up, you can put him and the water back in the bag and float it in the tank to get it up to temperature for 15 minutes then scoop him out and put it in the tank(not the water though). If the water in the bucket is already at the same temperature as your tank you can just scoop him out and put him in the tank without floating the bag.
The other method, and I would only do this with fish, is to float the bag in the tank, adding a small amount of tank water to the bag every 15 minutes. If it gets too full pour some out in the sink and keep adding incrementally from the tank. When you're done scoop him out and put him in the tank.
Make sure you never let the water he came in get into your tank, that's why the bucket is better. You will end up with whatever parasite or disease or chemicals that were in their tanks in your tank. Don't forget to qt
if at all possible to prevent sickness in your main tank.