I gather you do not want autologin. I looked at mine which does not autologin:
Originally Posted by Alex_Silva
So, my suggestion is to comment out the lines beginning with autologin (so they will be ignored) and see what happens. Put a # symbol at the start of each such line.
dn@Sydney:/etc/lightdm$ cat lightdm.conf
and the same with the other autologin lines.
I would use the nano editor in the terminal to make the changes. You need to practice using it a bit first. When you feel ready to proceed, cd in the terminal to the directory /etc/lightdm and sudo nano lightdm.conf to load it up for editing.