This question comes up more often than you may realize.
Most helmets have the brand name on the front.
Very helpful if yours is one of them. Virtually all helmets have the nape straps anchored at the rear. So the rear will be the end where two straps come almost together at the rim, or even join at the rim. When the helmet is correctly on your head with the front end forward, the furthest forward strap should come just in front of your ear and almost straight up to the helmet. If you have a strap coming around the side and angling forward across your cheek, you probably have the helmet on backwards.