[GMCPaul]

For the round heater outlet ends and the 1 round defrost vent end turn them clockwise as you go to put it on as though you are threading a bolt into a nut the spiral wound wire will then thread itself on to the end of the vent or heater box as you do this, make sure not to stop until defrost hose spiral wound wire has worked its way past the tabs that stick up to keep defrost hose on because if you stop without getting it on past these tabs it will just blow off shortly after turning the air on. The oblong heater defrost vent can be done somewhat the same but requires greater paitence. I've always found it easiest to install the heater box end first then extend hose so it sticks through top of dash and then install the defroster vent onto hose by rotating the vent onto the hose sticking up through defrost vent dash opening.
Paul @ GMCPauls