What's the correct way to pass wire to exterior electrical box?
The IRC or the NEC doesn't apply here, common sense does.  What you need to do is apply a paintable silicone acrylic or silicone caulk to the back of the box and around the entry hole before you screw the box to the wall. There should be holes inside the box or external ears for mounting.  The idea is to stop water from going behind the box and around the conduit into the wall.  Don't be afraid to use it, you can wipe off the excess with a damp cloth.  Good luck.