Take the lid off the coffee can with a manual can opener (the kind you have to turn with your hand). Be sure to use a manual can opener -- electric can openers will take off the inside lip, which you don't want removed.
Fill a washtub with room-temperature water and put the piece of goat skin in the tub. Let the skin sit in the water for an hour.
Adjust the hose clamp so that it is slightly larger around than the can. When the skin is ready, pull it out and center it over the top of the can.
Slide the clamp onto the can, over the skin. Tighten the clamp slightly, and then pull down on the skin on all sides. Gradually tighten more, continuing to pull until the clamp is securely around the can and the skin is tight.
Place the drum somewhere dry, such as a garage or closet, or outside on a warm, dry night, and let it sit overnight. Test the drum, and then trim the extra skin from around the clamp if you are satisfied.