Actually, with all due respect to spymerinator, you don't have to have StyleXP.
Once you've downloaded the visual style of your choosing, open up the zip and copy the folder out to wherever you want it.
Then take the folder, check inside to ensure it has a .msstyle file; in this case, it's in InspiratSE/Visual Style. You'll see 2 folders, and in each is the two style choices you get with this theme.
Go up a folder from Visual Style, and then copy the Visual Style folder.
Go to My Computer, then hit your main drive, probably (C
.
Go to your Windows folder and once there, find a folder called "Resources". Under Resources, you'll find "Themes".
Paste the Visual Style folder from InspiratSE in there, and rename it from Visual Style to InspiratSE.
Once you've done all that, go to your desktop, right click, and hit properties.
In the Display Properties window, go to the Appearance tab. Under the Windows and Buttons drop down menu, you should find your visual style, if you've done everything correctly.
;D Hope that helps.