These seals turn out to be a PITA to install. I even have several Ford Rotunda Essential Tools seal installers to work with and it is still hard. The dang thing keeps wanting to go in crooked. These large, plastic Rotunda seal installers cover up everything making it hard to see if the seal is aligned evenly with the bore.
Finally dug through all my Rotunda tools and came up with a large, flat-faced, steel driver that popped it right in. Stick the seal in place by hand first to get it as even as possible with the bore. Use any flat, driver face that is at least as large as, or larger than, the outer seal edges, then give it a quick whack to drive it home. This shouldn't this hard but then, its a Contour - is anything ever easy on this car?