How to join and register iOS device (iPhone) with Azure AD?

Explanation:
Go to HOME --> Azure Active Directory --> Devices --> Device settings.

Open Apple Safari and navigate to Azure Active Directory Device Registration service Over-the-Air Profile endpoint for iOS devices.
https://enterpriseregistration.windows.net/enrollmentserver/otaprofile/<yourdomainname>

Where <yourdomainname> is the domain name that you have configured with Azure Active Directory.

https://enterpriseregistration.windows.net/enrollmentserver/otaprofile/xavierdilipkumar.com

Open Apple Safari and navigate to the Device Registration Service (DRS) Over-the-Air Profile endpoint for iOS devices.
https://adf1s.contoso.com/enrollmentserver/otaprofile

1. Log on to the webpage by using a domain account credentials
2. You are prompted to install a profile. On the Install Profile screen, click Install.
3. When prompted to confirm installation of the profile, click Install Now.

4. If your device requires a PIN to unlock the device, you are prompted to enter your PIN.
5. The profile installation is finished when you see the Profile Installed screen. Click Done.
6. Return to Safari. A message informs you that you can close or leave Safari.

Goto HOME --> Azure Active Directory --> Devices --> All devices