Having a debate.
We have the Global Command Support System
Known as GCSS.
There is a Web-portal that users log on to.
access GCSS Portal.
access the GCSS Portal.
You access the GCSS portal.
It's not so much a proper noun as a descripton. It is the portal for the GCSS.
If you gave the portal a name like "Fred", for example, that really would be a proper noun. Then you would log on to Fred.