Go to https://manage.windowsazure.com and select Active Directory as shown in below screenshot. Click on any Directory where we want to add user or click on Default Directory.
Click on the Users link and verify number of users available in the directory. Click on Add User.
Select User with Existing Microsoft Account (Choose as per your requirement) and provide Email address.
Fill user profile with details and select Role for the user as well. Click on Right symbol.
User is added into the default Directory.