Not sure if there is any videos or picture guides of how to install these sheets out there, but it is a fairly easy process. I just kept the plastic on mine at first, measured of the size of the inside of the case, then drew that out on the plastic with a sharpie & straight edge, then just used scissors to cut the shape out. I measured off & cut out the hole for the reset button & USB port in the same fashion. Next I peeled the plastic & installed it in the case it was cut for, used a razor blade to cut slits in the sheet to allow for the stand offs to come through. After that all I needed to do was push any bubbles/creases out from under the sheet to make it lay flat & stretch the sides a bit to make sure it was covering the entire bottom of the case edge to edge.
It should also be mentioned that this stuff is super sticky once the plastic is removed, so be sure to have it placed well in the case before you install the plate/PCB. In a good bit of cases there is just enough room for a sheet under the PCB & the sorbothane will get stuck rather firmly to the bottom of the PCB after the plate/PCB has been tightened down on to it. Anyways, I know a video would be better but hopefully this helps you out some!