The best tip I can give you is look at both manuals and read them
And, if it seems like it can't work at all call your dealer and try and get more information. There are some seats that are a no fit for certain cars.
For yours shawn we had to use a locking clip because it is an older molder car and doesn't have an automatic locking retractor.
This makes it very difficult to ensure a tight union between your child seat and the cars seat.
We still need to get that seat tighter Shawn, but it is better then what you had it before.
I nearly made a mess in my pants knowing how it was.