I installed a special build from GraphicAll.org for blender. It gave me a .7z file after the download. How do I install this into blender or use it for blender?
You don't have to "install" that file into blender. That file IS a blender version! You just need to decompress that file with 7zip (http://www.7-zip.org/), a free open source compression/decompression utility which handles many formats. 7z is usually more efficient than .zip so is often used as alternative for big files.