External Internet Access by Sites and REST Manager

All the default charlotte sites require access to external map services like ArcGIS Online and Bing and Geocortex urls.

 

 

Ours by default aren't capable of accessing the internet.   e.g. we can't add arcgisonline map services to our sites.

 

 

What are the steps I that I need to go through to give Sites and the REST manager access to the internet (we have a firewall proxy in the way)?

 

 

Do I need the users Essentials or EssentialsAdmin to have internet access?