5. Open up the Windows Start menu again and this time type 'cmd' into the search box and press enter. This will bring up a command prompt. Welcome to Windows' long distant past. You can do pretty much anything from a command prompt, but we're going to keep this simple. For now, just do what I do: type 'cd C:\renders\mcobj' without the '. cd means Change Directory, by the way. Now type 'mcobj', and it'll run the mcobj.exe in the directory we're now looking at. This will pour out a bunch of instructions for what mcobj's different instructions do.
6. Let's keep keeping it simple. Now type 'mcobj -cpu 4 -s 20 -o world1.obj C:\renders\[savegame]' where [savegame] is the name of your saved game. This will use 4 CPU cores (change the number if you don't have a quadcore processor) to output 20 chunks of your saved game immediately around the spawn area, and will create it in a file called 'world1.obj'. There's a bunch of stuff you can tweak: rendering areas other than the spawn, or larger areas, or underground areas, and so on. For now, press enter, and a pouring stream of text should appear as it turns all those Minecraft-y blocks into a renderable 3D model.
7. Install and open Blender like you would any other piece of software.