Absolute power.

Could you please tell me how to launch a map? I placed the file in the Maps folder, but it doesn't appear when selecting maps in multiplayer...

I assume you put the archive directly into the Maps folder. In reality, there are 3 files inside the archive, and the one with the .h5m extension is the one you need to place in the corresponding folder.
If you did everything correctly, it should appear – I don't have any problems (I just checked).