You can do this by:
- Logging into the Azure Management Portal
- Select
Settings
on the bottom left - Select
Administrators
at the top of the screen - Click
+ Add
at the bottom of the screen - Enter a Windows Live ID or Microsoft Account into the Email Address column
- You can create a live account with an existing email here
- Select the Subscription(s) you want available to the user
- Click
OK
Poof! You're done!
You can find the full article here