To run the server in primitive plus all you need to do is to log into your Clanforge service and navigate to:
Clanforge>Edit Profile>Setting

On the left side you can find a link that will direct you to the text box

You will then find a text box which will initially be empty but you can activate primitive plus by typing in or copy+pasting: 111111111

Once you have completed that you can Save & Apply which will restart the server and start it up using Primitive Plus instead of the standard setup.