I am trying to set up a new portal, can you confirm what the portal URL should be?

As an example, if you own the domain 'xyz.com' then you can have the portal URL as 'support.xyz.com', 'sales.xyz.com' etc. The same needs to be created as a CNAME pointing to 'yourcompanyname.freshdesk.com' in your DNS. You will need to create a TXT record in your DNS as well that would be similar to 'fdkey.support.xyz.com' or 'fdkey.sales.xyz.com' pointing to the values displayed under Admin--> Multiple Products--> Settings.