How to get back the sudo priviliges?

[Vainio Juhani]

I am a newbie. Installed kubuntu. Everything was OK, until I thought to change
my password. I did it yhe following way: In KDE i Clicked System, then KUser.
Then Opened window and there was button Change Password. I changed it. Then I
logged out, but could not log back in. Kubuntu said, that I had root priviliges
and I could not log in to GUI.
How to get back the sudo priviliges? I can go to the teminal and there get the
root privileges, but I dont't know what to do there.