To add an administrator to the Azure portal, it has to be given the owner role. It will be able to manage only those resources in the subscription that are assigned to it. To add an administrator, follow these steps:
Sign in to the Azure portal
Go to the Hub menu and then to Subscription and select the subscription that the administrator will need access to
Select Access control (IAM) in the subscription blade, and then click on Add
Go to Select a role, and click on Owner
Here, provide the email address of the user to be assigned as the owner
Click on the user, and then click on Select