I'll give you an answer, but first here's a warning.
It's dangerous to do this, and usually not recommended at all; you're better off using
sudo. I myself have had my system destroyed this way when I was kind of new to Linux.
However, here's how you do this if you really want to risk a broken system:
- Fire up a terminal
- Enter your password
- Enter a secure password for the
root user (different from your main user)
- Repeat the password
nano /etc/lightdm/lightdm.conf(replace nano with the text editor of your choice)
to the bottom of said file.
If you followed these steps you should be able to login as
root, but as I said before: don't do this if you don't know what can go wrong.