I suppose that depends where you're from. In the United States, you can just go to any store that sells them. They usually give a bit of a discount for the new tank if you turn in an old one, and it doesn't matter if it's expired. They send it back to the manufacturer to be dealt with.
The procedure to exchange the expired propane tanks is to open the cover of the tank and remove the drained propane tanks. To do this, you will need toiak the tank, then with both hands, remove the drained propane tanks from the top of the tank.
