Answer:
You need to download the file, unzip it and copy it to your minecraft folder. The full guide can be found under "Sources and related links" below this answer.
First, download the map. Next open your star menu and type in: %appdata% that'll take you to Roaming. Click on the folder .minecraft, click on saves, and unzip the map into that folder. Next, open minecraft and play it just like any other saved game. =] Hope this helped, ~Damoknight