Alright, so download each of those files and unzip them, assuming you're using Vista or 7 then move those files to your Documents Folder->Rainemeter->Skins. Right click on one of your Rainmeter widget things and click Refresh All. Now right click again and go to Configs, from here you can add any skin that you've put into that folder up there ^. Find the ones you've downloaded and add them. The Enigma ones should be already there.
If you want to change the colours on your skins at all just right click on the one you want to change then Skin Menu->Edit Skin. The colours are in R, G, B, Opacity format, just use photoshop to find out the code for your colour. Genreally Opacity will be 100% so just leave that blank unless it's a background.
It takes a bit of getting used to but once you work it out its a piece of cake. Does the wallpaper download work fine?