What exactly are you having a problem with? The C-M-17-IMP base is made so that you don't use the seat posts as attachments, nor do you have to remove the seats to get it in.
I have a Trak-Mount using the same brackets installed in my '04. Here's how it goes in:
Driver's side
Passenger side
edit: Okay, I see what's going on. Your kit came with those little "fingers" that go underneath the seat post's hinge point to hold the base in. Mine didn't come with those, and I sank sheet metal screws in the three holes to hold it down.