How will you add a client to server? How’s the client joining a domain? What are the client configurations?

You can connect a client to a server by simple making the client belong to the same network as your server. It could be via LAN or WAN. A client can join a domain by Static or DHCP configuration. If it's a DHCP Server then the client can simply obtain the IP address from the server, but if there a specific rules in terms of access list, then the client should have a valid configuration that the server sets to make the client pass or have access from the server.