It used to be available only by prescription (most commonly for women’s yeast infections) but is now available OTC. And it’s the same stuff whether used for women’s yeast infectiins, ringworm, jock itch, or athletes foot.
You can find it on the regular shelves at any drugstore or the pharmacy section of most grocery stores.
It’s available in both cream tubes or as a spray with powder.
A brand name I prefer is Lotrimin because I’m familiar with it but you can also get generic versions.
There is no age restriction. Just pick it up off the shelf and go to the checkout counter. No problems.