Take a light stick/glow stick and break it to mix the chems then cut it open and put some on your body? lol I have no idea. That might cause a chemical burn. There is glow-in-the-dark paints and colorings and crayons etc you might be able to dot your skin with, but I'd certainly test a skin patch first to make sure you don't have a reaction.

Or, simply join the FBI and you'll glow for the rest of your life!