What do I do with a map file to play it?

That depends on what you want to play with:

• With the aLobby
  • Solution 1:
    1. Start the aLobby as usual.
    2. Search for the desired map via „New Game“.
    3. As soon as you start it here, the aLobby downloads the map and stores it in your Settlers 3 installation.
    4. Done. You can start the map immediately via the aLobby.
  • Solution 2:
    1. Start the aLobby as usual.
    2. Call up the mapbase and search for the map you want.
    3. Click on the download of the .map file.
    4. Confirm the hint to the protocolHandler that your browser shows you.
    5. The aLobby downloads the map for you and stores it in your Settlers 3 installation.
    6. Done. You can start the map immediately via the aLobby.
• Without aLobby
  • Solution 1:
    1. Call up the Mapbase and search for the desired map.
    2. Click on the download of the .map file.
    3. Click in the hint window on the direct download to the file.
    4. Save the file in your download directory.
    5. Now call up your siedler 3 installation directory.
    6. Now copy the .map file from your download directory into the subdirectory map/user/ within your Settlers 3 installation directory.
    7. Done.
  • Solution 2:
    • Hint: For unpacking you may need a packer program. At least in Windows 10 this is already integrated.
    1. Follow the same steps as in Solution, but download one of the ZIP files.
    2. After step 4, unzip the file.
    3. In step 6 you copy the unzipped ZIP file into the described directory.
    4. Done.