That's an untextured Minecraft Azeroth render above.
3. Open up the Windows Start menu and in the Search box (or by clicking 'Run', if you're on an old version), type '%appdata%' without the ' and press enter. This will bring up a hidden folder on your computer, normally C:\Users\[Username]\AppData\Roaming. In there, you'll find a folder called '.minecraft'. This is where the blockbuilder installs all its files. Hop inside, and then into the folder called 'saves'. Here are all your save games. Copy the one you want and paste it somewhere else on your computer. Let's say 'C:\renders\[savegame] where [savegame] is the name of your, uh, saved game.
4. Open up your mcobj zip, and extract it somewhere on your computer. Let's say C:\renders\mcobj.