The public SSH keys from cliens that which to SSH into the machine will be placed in the ~/.ssh/authorized_keys file of the root user's account. This will allow you to log into the server from the computer with your private key.
To view the public keys to add to the ~/.ssh/authorized_keys:
cat ~/.ssh/id_rsa.pub
pbcopy < ~/.ssh/id_rsa.pub
Created on 2/17/2019