Step 1- lay bottom towel rack and wall mount on its end as shown.

Step 2- insert bottom shelf onto nipples

Step 3- lock bottom shelf into place with couplings. - Hand tighten only needed.

Step 4- add 6" pipe plus coupling with nipple at end to both sides.

Step 5- place second shelf onto nipples and lock into place again with 2 couplings

Step 6- repeat step 5

And done !