How to register domain on Akamai. (Akamai CNAMEs)

So I was wondering if any of you could provide some insight on Akamai CNAMEs and how one can register them.

Let's say I had a subdomain:

testcdn.domain.com -> CNAME -> testcdn.edgekey.net

My question is, how does someone register testcdn.edgekey.net on Akamai?