Here's a guide on how to install downloaded AFPD sceneries from the various free websites. This is a drag-and-drop method which I find is easier and faster, compared to unzipping.

Most downloaded sceneries come in the form of an executable file, and all you have to do is to double click on the downloaded zip file, then double click on the scenery .exe file and this will automatically install it into AFPD. An example is shown below