OpenSSh on Ubuntu/LinuxMint
To install openSSH, open terminal (Ctrl+Alt+T) or log in Ubuntu server and run command:
sudo apt-get install openssh-server
After that, you should have SSH service enabled in your system, you may check its status by running command:
sudo service ssh status
You may change some settings (e.g., the listening port, and root login permission) by editing the configuration file via command. Otherwise if you are happy with the default settings, you are done!
sudo nano /etc/ssh/sshd_config
Finally apply the changes by restarting or reloading SSH:
sudo service ssh restart
On LinuxMint
sudo apt-get install openssh-server -y