I just put some in a couple of weeks ago. I'm sure there is a better way, but this is how I did it:
The retaining clips have a sharp ear like jagged corner on two ends ( the top), and a curved, rolled sort of edge on the other end (the bottom). Those ends face outward. My rivit tool had a face that was larger than the opening, of the clip edges, and would not allow me to get the rivit to contact the clip. So, I used a little nut as a spacer between the rivet head, and the rivet tool, and all worked well. If you put the clip up to the trim piece, you will notice that the sharp eared corners will slide under the inside lip edge of the trim piece, and the bottom will then kind of 'snap' into position. This shows how it will be on the vehicle. Next I placed them i order, loosly placed the sole retaining screw and nut, the kind of one by one, working one end to the other, 'thumb pressured' the molding into the clip. They quietly snap into place and 'lock down'.I had to use a rubber mallet gently a couple of times. The clips need to be aligned as perfectly as possible, or its a problem getting them to snap in. I dont know if this is the correct way, but it worked for me. And they are tightly in place.
PS: I didnt enjoy this kind of work, and hope I dont have to do it again. It was tough drilling into new paint and those sills!