Prerequisites:

Organization should exist

AAD users must exist.

Add AD users to the Organization

Step 1: Connect your Organization to the Active directory. Organization Settings –> Azure Active Directory and select the AD to which you want to connect.

Step 2: Once you are connected with the AAD then Organization Settings—> Users

Step 3: Add users by clicking on ADD Users button.

Step 4: Once the users are added then provide the permission to the users. Organization Settings –> Security –> Permission and provide appropriate permission. You can connect to Azure DevOps with the added user and change the permission to see how the user can access the DevOps Projects and other resources.

Step 5: You can set the permission on the project level.Project settings –>General–>Permission and select permission you want to provide to the users.