For the car seat, you just buckle it in, in the slit type thing, like you saw in my pics. Then you lock the seat belt, which varies depending on your car, but usually you lock the belt by pulling out all the slack in the shoulder belt, then letting it go slowly, and you'll hear the shoulder belt ratcheting up. Then you pull it tight, and the seat will be nice and tight in it! In my car I had to take a blanket, and fold and lay it underneath the seat where it buckles, because otherwise it would kinda flip up cuz of having it nice and tight. Then you just buckle the straps for each pup around the lap belt, then hook it onto their harness!
If you need me to take a video or anything, I can.