Hi, please see these two links, this can be implemented in a number of ways but usually includes setting up Azure AD Connect and implementing hybrid identity with the chosen method discussed in here, the second link also includes some recommendations towards the end (this isn't to replace Active Directory but to extend it into the cloud and Azure AD):
"Microsoft’s identity solutions span on-premises and cloud-based capabilities. These solutions create a common user identity for authentication and authorization to all resources, regardless of location. We call this hybrid identity."
@Mani000 For a list of steps, check the installation roadmap as a place to start - Azure AD Connect and Azure AD Connect Health installation roadmap.