End-users must perform this step before installing Windows 10 Enterprise.
(For end-users that are installing Windows 10 Enterprise to a new device should follow the instructions here.)
1) Open ‘Settings’ on the device
2) Select Accounts > Access work or school
3) On the ‘Set up a work or school account’ page select ‘Join this device to Azure Active Directory’ under Alternative actions
4) On the ‘Let’s get you signed in’ page enter the Azure AD credentials and click the Sign in button
Now the device is Azure AD joined to the company’s subscription.
The end user can log in to their device using the Azure AD credentials and the Windows 10 Enterprise E3 license associated with the user will enable Windows 10 Enterprise edition capabilities on the device.
Refer to this article for troubleshooting common activation issues.