You can turn whitelist on by following the steps below:
1. Log into the Multicraft at mcp.fallout-hosting.com.
2. Stop your server.
3. Go to Files - Config Files - Server Settings in the Multicraft panel.
4. Find where it says Whitelisting and then using the drop down menu next to it select Enabled and click save at the bottom.
Now when your start your server it will be whitelisted.
To add a player to your whitelist: /whitelist add <playername>To remove a player from your whitelist: /whitelist remove <playername>