Enter the IP address of the remote host in "Host Name (or IP address)" field. Default port is 22, if you have not changed it during SSH server setup. You can enter a name in the field under "saved sessions", and click "Save", so you can use the setting next time without typing everything again.
Click "Open" to connect to the remote host.
You will see this alert in the first time. Click "Yes. If you see this again in the future, it means something has changed. (e.g. IP address of the remote host) You should pay attention if the change is normal.
Enter "username", hit ENTER. Private key will be used automatically.