Line the back of the diaper up with the belly button general area. Pull the front of the diaper up between baby’s legs and fit it up in the leg creases.
If you’re using rise snaps, fold the “pocket” upwards and tuck the wing a bit so the crease makes a nice line all the way across the front of the diaper. This will make for a nice, neat fit.
Snap the diaper so it’s snug around the legs and waist, but you should be able to fit your fingers inside without too much trouble. On diapers that have two vertical snaps, the bottom snap is for the legs and the top is for the waist. These snaps don’t have to be in line – you can stagger them (does that make sense?) if you need the waist tighter, but the thighs looser. On diapers with two horizontal snaps, the inner snap is for the legs and the outer snap (closer to the tips of the wings) is for the waist.
Check and make sure the diaper is in the leg crease where undies would go, and that all the diaper innards are inside the cover.
Check the back to make sure diaper innards aren’t coming out.