A white list is your primary means of preventing unauthorized entry into your server. Any official Minecraft usernames that you put in this list will be allowed to enter your server, while anyone not on it will be denied access.
ACTIVATING/DEACTIVATING THE WHITE LIST
In order to activate/deactivate the white list, you must first log in to your game panel. Once in, click on “Configuration files”. In the server config, you can enable or disable the whitelist. Make sure to restart your server after saving the settings on that page.
ADDING USERS TO THE WHITE LIST (File: whitelist.json)
You can edit the white list file by either editing it in the File Manager or editing through FTP.
IMPORTANT: Before you can add a user to the whitelist, make sure to first allow that user to join your server with the whitelist off so that the server “knows” their UUID/username. Once that is done, you will then be able to re-enable whitelisting and add them as described below.
You can also add a user via console or in the game itself. To edit via console, you will need to click on “console” in the game panel under the navigation menu. You can add users to the white list by typing into the console the following: whitelist add username
To add the user in-game, you would follow the same format: /whitelist add username
This method does not require a restart.
EXAMPLE SYNTAX / FORMAT FOR THE WHITELIST (You can get uuid’s from here http://mcuuid.net/)