That's easy if you have the right directions. Unfortunately all they gave u was a diagram and no literal instructions. Having just done this for the AllJs shelf I can point you to those directions:
http://www.youngs.org/kjparts/all-jrack.pdf
The info u want is on
PAGE 4
The install is the same except they didn't give you any washers to put between the bolt (A) and the holding nut (also A). The washers just help to reduce the friction when u do the install.
Basically, u drill a hole (unless it's already there, which it may be in your case), insert the threaded insert which is on the end of that (A) bolt (which they call an install tool), hold the nut closest to the body where the insert is with one wrench to keep it from turning or pulling out, and tighten the bolt (A) with the other wrench.
This causes the insert to expand inside the hole. When it is tight you unscrew the bolt/install tool (A) and u r left with a threaded insert inside the previously empty hole. You repeat this for the other holes using the same bolt/instasll tool. When u r done these are where u will screw ure mounting bolts to.
_________________
My pics!!'03 Rennie w/all Tupperware
Custom Roof Basket
Mopar Tubular Brush Guard
Garmin GPS V & Laptop w/Nav software
RAM products laptop mount
Maglite w/mount
Rear cargo bay tool cabinet
AllJs Rear Shelf
Rear receiver
250k miles!
LOST #CR051230