[Carlton]

Those are the right screws, but those bottom pieces don't go on that rail, they go onto the bottom bracket where the bolts attach to the floorpan. You press them into the carpet and then the one screw will hold them down properly.
As far as I know, nothing goes into that one hole you have the screw threaded in to.

 

[Carlton]

No, the hole is in the lowest seat bracket. Once the seat is bolted in, put the cover over the bolts and it will be obvious.