User accounts have no subscription assigned

I have created 3 user accounts in Azure Active Directory (from Azure Management Console) to give access to my developers to the AZURE management console so that they can work on various elements (DB, virtual machine, mobile services, etc.).

However, when I try to log in using the newly ceated user account, after the successful suthetication, I get an error message that no subscription has been assigned to the user.

However, I do not see any option to assign a subscription to the user during account creation.

I wan to give these accounts access to all the modules that have already been created under the master account (my account).

How can I resolve this issue?

Thanks