How to seal bath spout nipple?
So the adapter ring (the split threaded nipple) slips over the stem (the piece with the rubber O-rings). The stem is pushed into the supply pipe (in the wall). To connect the stem to the supply pipe the split threaded nipple is tightened until the stem is snug (the flat spots on the split nipple are there for a wrench). Next try sliding the chrome eschuteon plate on the stem and bring it to the wall. You should be able to fit the spout on to the stem and secure it to the wall plate.