Okay, many new people have been wondering how to install maps.  If you are one of them, you've gone to the right place.

The first step is to download the map that you want.

Next step, press the windows button and the r button at the same time.

A message should appear witha search box.

In that search box, put in %appdata%

Now, once the download is done, you want to open the file.

Once the file is open, there should be a button that says "Extract all files".  You want to press this button.

Now that you've pressed it, a search box should appear again.

Going back to the %appdata%, press the .minecraft file.

Enter the saves file.

Now, go back to the file you put in and copy the exact directory you can see in the .minecraft folder.

Press extract.

Now, when it's done, you want to open minecraft.

In the singleplayer mode, if all is done correctly, it should appear in the maps.

Enjoy!

Also, this is my first tutorial, so be nice, please.
*I may do a Mac tutorial later, but it will be hard since I don't have a mac myself.*