Once you have added your server to the Federated Network you can talk to users from server who have done the same.
After enabling federation, you should be able to start chatting with other servers.
To do so, you should go to the
Users tab, and pick
Every Workspace from the dropdown menu.
Then, you should be able to look for users on remote servers, called peers. You can search using a combination of a username and a domain or an e-mail address, like:
If the remote server is within Rocket.Chat Federated Network, you will be able to see the users:
If you click on one of those listed users, you will invite them to your server without login access. Also, you and everyone else on your server will be able to chat with that new remote user.
From now on, you can invite that user only to private rooms or discussions. Those channels are going to be replicated to the remote server, without the messages history.