Jarrett, in my opinion, it's actually quite simple. You attach an "inner" top rail to the lower edge of the mobile home with nails or screws (screws much preferred, in my opinion). The "outer" top rail will then just snap into the inner rail after you install the vertical panels. In most cases, you simply measure the height from the ground after the mobile home is completely set up (installed). Of course you have to cut the vertical panels to the proper length, but you have a considerable margin for error; i.e., they don't have to be exact. The bottom rail is frequently just laid on the ground and held in place with big nails or spikes into the ground. Another way to do it is to lay landscaping timbers all the way around with them anchored to the ground, then nail or screw the bottom rail onto the landscaping timbers. In my opinion, the worst thing about vinyl mobile home skirting is the fact that a string trimmer will chew it up very badly and very easily. Using the landscape timbers is one way around that problem. Another way around it is to use another outer top rail, turned upside down and snapped into the bottom rail. String trimmers won't hurt the rails. Some installers put one screw in both the top and the bottom of each vertical panel. IF the mobile home should settle, the panels will buckle, and of course, you have to remove screws if you ever need to get under the mobile home, so I prefer not using the screws unless strong winds make it necessary.
Cutting the vinyl can be done with scissors, tin snips, or a variety of saws. The fastest, easiest, neatest cutting I ever did was with a radial arm saw, although a regular hand held circle saw works very well. A little sabre saw will work, too, but it's much slower.