CDN Edge Groups

CDN edge groups are groups of edge servers – your own, and those you subscribe to from the CDN marketplace. They are usually grouped by location, so they represent a pool of servers for a given geographical area. Once you have created an edge group containing edge servers in specific locations, you can then assign the group (or groups) to a specific CDN resource.
The CDN edge groups menu enables you to see available edge server locations and form them into CDN Edge groups.  

You need to associate CDN Edge groups with buckets to make them available for users.