You slip the silicone gasket over the fan side that will be against the panel. It's that simple. You've got three options with the screw mounts: put them between the panel and the silicone gasket, between the silicone gasket and the fan (we'd try this one last), or on the outside of the case between the screw head and the side panel(this is the one that the product page says to use). We suggest trying them out to find out which one works best for your case.

The silicone solution greatly decreased the audible vibration we were getting. It eliminated that vibration and immediately we could tell the difference. If you're having medium to big vibration issues and have narrowed it down to a fan, this is probably your best choice to straighten the kink and get your ears back to picking out the footsteps down the hall in between the gunshots instead of the gunshots from the vibrations.
The next solution is a little smaller, a little cheaper, and works pretty well. If one of your fans is vibrating, maybe not a lot, but enough to make a noise you might want to look at these. The Soft Gel Mounts go into the screw hole on the case, smoosh them in there, and they provide cushioning and a snug fit. If you've got fan mount holes that are a little too big, trying these might just be the quick fix to your problem. For smaller vibration issues, especially those directly related to the mounting screw, we'd try these.