This will tell you how to install Extinction DLC on GTXGaming.co.uk's control panel.
1. Login to our control panel https://www.gtxgaming.co.uk/gamepanel/
2. Run the Steam update, the DLC will be around 20GB in total and may take some time. Wait patiently for the Steamcmd download to finish. If it says its up to date and you know it has not downloaded anything, try deleting the steamapps folder in the file manager and then running the Steam update again.
3. Go to configuration files on the control panel.
4. Click Easy Configurator on the Config.bat and choose Extinction in the drop down menu and click SAVE.
5. Then go to the main game server page and click WIPE SERVER as you will need a fresh server for Extinction.
Please note that a lot of existing mods may not work or function correctly with the Extinction map so please take this into account when changing to Extinction. At first it might be advisable to have a vanilla server while the mod developers fix any bugs.