How do you remove urine odor from skin down there?

Hygiene. If you are talking about usual urine odor that is present in some folks, i would suggest to exercise proper hygiene, to begin with. After each urine passage, you will need to wipe yourself from front to back, either using a wet hand or toilet tissue. If it is still the problem after you've done it, you will need to use more water (get in the shower) and rinse whatever remnants of urine are hiding.