To position the pads before you insert them into the bicycle shorts or bibs you must know your exact sit bone distance. There is an easy way to find this distance out yourself without going to the local bicycle shop to have them measure you.
Take a piece of corrugated cardboard and put it on a hard flat surface like a piano bench. While sitting on the cardboard have your feet propped up off the floor on a shoe box or skateboard. Your sit bones will leave indentations in the cardboard. Rub the surface of the cardboard with the flat side of a piece of chalk or crayon and those indentation will appear visible. Mark the center of each indentation and measure between the two of them. That is the distance of your sit bones apart from one another (your sit bone distance).
Velcro the pads together at your sit bone distance, measuring from center line to center line.
Unzip the hidden zippered pocket in the back of the pump shorts or pump bibs exposing the Velcro (looped) material inside the pocket. Press the pads with the strips of Velcro (hooks) on the pads firmly onto the exposed Velcro looped material of the shorts of bibs. Glide the pumps with the air release button through the channels of the shorts and up through the waistband until the button for the release valve protrudes through the holes in the waistband. The elastic material around the hole of the waistband will catch under the air release valve of the pump locking it in place at the hips. Having the apparatus properly situated and locked in place, you can now zip up the back of the pump shorts or pump bibs.