Thank you for asking this question on the Microsoft Q&A Platform.
If those domains are in the same Domain Controller You should install Azure AD Connect on your server https://docs.microsoft.com/en-us/azure/active-directory/hybrid/whatis-azure-ad-connect
Azure AD Connect is an on-premises Microsoft application that's designed to meet and accomplish your hybrid identity goals.
You can follow these steps https://docs.microsoft.com/en-us/azure/active-directory/hybrid/how-to-connect-install-express
If those domains are in multiple domain controllers, you should follow any of the topologies described here --> https://learn.microsoft.com/en-us/azure/active-directory/hybrid/plan-connect-topologies#multiple-forests-single-sync-server-users-are-represented-in-only-one-directory
Hope this helps!
Accept Answer and Upvote, if any of the above helped, this thread can help others in the community looking for remediation for similar issues.
NOTE: To answer you as quickly as possible, please mention me in your reply.