Unable to create alias to my user

Unable to create alias to my user

I ( demetriusjk@zoho.com) recently signed up and are tying to learn the features. I have not yet changed the MX because i cant create an alias named "demi". I created one at first called "deme" and that worked but as you can see i misspelled.

I get a red popup saying:
Alias Email Id already registered by user not belongs to your organization.
How can a user with my uniqe domainname be located somewhere else?

How do I create demi@diamondglacieradventures.com alias to my user-account?