These steps will let the user that you create ssh to a running instance using a password you set. The user can reset the password once they login and/or add their ssh keys.
All steps to be run as root or using sudo. <USERNAME> should be replaced with an actual username
- Sudo or otherwise become root: sudo su -
- Create the user: adduser <username>
- Assign a temporary password: passwd <username>
- Add the user to group "users" : usermod -a -G users <username>
If don't do this step, you'll get a "connection denied" message when you try to ssh in.