You can connect to your REMOTE-SERVER ["REMOTE" as in a computer far away from you] via SSH/OpenSSH & for that to happen, you need your USERNAME & an IP-ADDRESS of the server you are connecting to. [All the REMOTE-SERVER needs to have is an SSH-Server-Component already installed on it]
ssh USERNAME@IP-ADDRESSOR ssh IP-ADDRESS
When you connect to a server via SSH for the FIRST TIME then it asks for CONFIRMATION by asking:-
Are you sure you want to continue connecting (Yes/no/[fingerprint])?
It basically allows you to Cross-Check whether the server you are connecting via FINGERPRINTS which are usually in these formats/standards of [You only have to accept the connection ONCE]:-
RSA
ECDSA
ED25519
The fingerprints of the servers whose connection you accepted will be stored in a file called "known_hosts" in the ".ssh"-Directory [Which is a hidden folder in linux distribution]. This Local-Copy of the fingerprints & IP-Addresses of Remote-Servers protects you & your "SSH-Client Component" from a M.I.T.M-Attack [MITM = Man In The Middle]
You can edit this "known_hosts"-File if you want to ADD/REMOVE Remote-Servers.
Now in order to disconnect from the Remote-Server just type "logout" & if the Remote-Server uses a "PORT" other than "PORT-22" then you can specify the PORT-NUMBER via "-p"-FLAG, as shown in the following example:-