gcoll,
On the BJ8, the first thing you need to do is make sure all the male ends are properly located and fastened to the car. If you installed a new interior at some point, you may have missing, lose or incorrectly positioned fasteners on the car.
With the top all the way down, start by laying the boot cover over the top. Get it the correct position. It helps here is you have another person who can hold the cover down on one side, while you do the other. Try to get it centered so that you are positioning the snaps at the same location on either side with the same margins between the edge of the cover and the snap. Pay attention to the center snaps and make sure they will reach when the side snaps are in place. You can pull the ends so tighe that the center snaps won't reach.
When you have it right, mark the center of each snap location with a silve colored sharpie. Just put a dot on the pint where you can feel the male end through the material of the cover.
Now you need to install the two piece female sides of the fastener. Get yourself a good hole punch and punch out the holes. Trying to do this with a razor knife can be dangerous to you and the cover. As I recall, the tennex fastener is a single hole installation.