Here you get help to open the files you can download here!
Themes: when the file is downloaded it will not be possible to open it! so then you copy/move the file on a USB pin and the you put it in your PS3 then you go to options and choose themes then you choose install! then you choose the USB you has inside the ps3! then you can install the theme(s)
Fonts: if you use Windows 7, you just open the file and click on the install button, but if you use windows vista or XP you need to go to your control panel! and search after "Fonts" when the search is done open the folder "fonts" then you copy the font you downloaded it and paste it in the folder! and then it's installed! but be careful if you delete a font it's hard to get it back for free!