What Bloo said.
my_presets is for you to make your own presets.
.material files are opened in notepad.
When you download one it'll be a .fhp file, which you put in the presets folder (not my_presets).
When you download one, it's only for you to be able to see the user wearing it, not to be able to use it yourself, unless the download contains the image and material files.