How to enable SSH access for user accounts? Log in as root; within /etc/passwd change the default shell entries of the resp. user accounts from /sbin/nologin to /bin/ash.
The resp. user accounts may want to have their public keys get placed in their .ssh/authorized_keys2 .
Of course the firewall needs to get opened a little on the local side for that – there is already a configuration for that, it is called “Encrypted terminal service (includes SFTP)“.