To attach the upper part of the shoulder strap simply thread the 2" webbing through the slider from top to bottom. Then, and this is the key, run the webbing back up and over the buckle and thread the webbing through the top of the buckle again. This will bring the 1" tail to right near the 1" buckle that actually does all the holding. Look at the pic real close and follow the threading pattern. If you don't do the second pass with the 2" webbing on the top of the buckle, there will be an uncomfortable gap in the connection of the shoulder strap to bag since the shoulder strap will hang too low. When done correctly, the padded part of the shoulder strap should be snug up against the body of the bag.
The bottom of the bag has two brightly colored tabs sewn into the underside of the main haul straps. The idea is to girth hitch the 1" webbing around the main haul straps and through these tabs. Just using the tabs will not be as strong or as stable. Just using the main haul straps will pull funny on the lower bond stitching where the main haul straps are attached to the bag.
This is what it should look like when attached properly.