Before proceeding you need to ensure your input (Sky/Virgin/TiVo/Kodi/Dish) is named Sky, TiVo, Kodi, or Dish (for Virgin please name the box TiVo) for the IP option to appear. Once named please ensure you 'save changes'.
When you have renamed the Input you can once again click on the input and you will now see an 'IP Control' box is visible (see picture below). Please proceed to input the IP address of the input (not the matrix) and select the product you are using from the dropdown menu. This will enable CEC to work.
Once you have inputted the details please ensure you click save changes and then proceed to reboot the Matrix for the changes to take effect.
Should you wish to name the input something else you can now go back into gotomymatrix.com and edit the name(s). The IP drop down will disappear but it will still be saved so do not panic.