If the device is already hybrid joined, you can use the automatic Intune enrollment policies.
"You can use a Group Policy to trigger autoenrollment to Mobile Device Management (MDM) for Active Directory (AD) domain-joined devices.
The enrollment into Intune is triggered by a group policy created on your local AD and happens without any user interaction. This cause-and-effect mechanism means you can automatically mass-enroll a large number of domain-joined corporate devices into Microsoft Intune. The enrollment process starts in the background once you sign in to the device with your Azure AD account."
Manual enrollment options
https://learn.microsoft.com/en-us/windows/client-management/mdm-enrollment-of-windows-devices
You also need to meet the other requirements for the user/device to join the device to Intune.
License, in scope for enrollment, etc...
If your still having problems with enrollment, please provide the errors you are receiving.
https://learn.microsoft.com/en-us/windows/client-management/mobile-device-enrollment