Attach the appropriate size saw bit to your hole saw according to the manufacturer instructions. Check the resources section for hole sizes appropriate for the type of bird that you want to attract.
Clamp the gourd down on your work table. Or, have a friend wear a pair of thick work gloves and hold either end of the gourd firmly to steady it on the table. Both of you must wear goggles and a dust mask.
Turn the hole saw on according to the manufacturer instructions.
Drill a hole near the center of the widest part of the gourd at least 2 inches above the bottom of the gourd.
Turn the drill off and pull the hole saw out of the hole. If the hole saw won't come out easily, reverse the direction of the drill while you pull it out. Don't yank or force it. You'll likely break the gourd.