If you like to swim, enjoy the pool. If you hate to swim, then avoid jumping in the water.
Download the .rar file, right click on it and extract it to /Documents/Skillwarz/Maps.
When the extraction has finished you can launch the game.
After login, click on the "Editor Maps" button from the menu.
Click "Add" and "Online".
Congratulation, you created your first custom map lobby!