By default SSH is not enabled in Retropie. Lucky for us though this is straightforward and easy to setup.
To begin with boot up your Retropie. Open up your settings and select “Raspi-config”. Here you can enable SSH and do other things like change your password, set boot options, overclock, and more.
Select “Interfacing Options” (the 5th option) on the following menu to configure connections to peripherals.
Next select “SSH” (the P2 option) to enable the remote command line access via SSH.
It will ask you if you’re sure that you want the SSH server to be enabled. Select “Yes”.
After doing so Retropie will inform you that the SSH server has in fact been enabled.
You’ll be brought back to the first Raspi-Config screen. Select “Finish”.
SSH has now been enabled in Retropie, but you’ll need to restart for it to take effect. Press “Start” on your controller and select “Quit” from the manu menu. Select “Restart system” and your Retropie will reboot.
After it’s finished, your SSH will be active and capable of use.