Hang it on your shower curtain rod, run a hot water only shower to steam up the room and close the door.

PS: A “make out” session in the steamed up room while you wait for the flag to relax is a great way to not let all that steam go to waste.

Wash and dry it, then hang it up again. If it’s not washable, hanging it in a bathroom with a shower may help to steam the wrinkles out over time.