While playing the game, press + ~ or to display the console window. Start the game, go into the options, then select 'Custom Maps'. Cut and paste the file back into the 'Maps' folder. Rename the map and put 'cus' before the name. Select a map file in the 'maps' folder in the game directory (for example, 'LowerParadise'). Note: This procedure involves changing a game file create a backup copy of the file before proceeding.