Car seat installation for dummies

Oh my......Y'all should have seen Todd and I trying to install the car seat base last night, talk about funny! We tried everything and that sucker still moves, I sat in it, I got in it and tried using my knees, all while Todd pulled the seat belt, then we switched, Todd got in it and I pulled the seat belt. What is the trick? I know there has to be one, right? I know when we get it in place that sucker isn't coming out until we get the one we registered for.