Initial Setup of FortiManager Behind a WebProxy

Normally when setting up a FortiManager we put it on the network and it just gets access to the internet. I am currently working on a customer where they do not allow direct conenctivity to the internet, It must go through their web proxy.

I can not access the GUI and I need to connect it to the internet to register it as a free trial. I have trawled the CLI manual about to setup a web proxy but I am struggling to find anything. Has anybody got any ideas on how to setup the web proxy from the CLI?