How to install user to sudoers during install, when root cannot login

Just installed calculate. But cannot login as root.
hd is working for about 20 min. Then light turns off. Nothing happens. Only option is to restart.
So I did a new install, but cannot add my user to the sudoers during install.
Hhmmm, out of knowledge. Yes, I can chroot.

sudo adduser gsdgsl (all) all 


From community got the hint: login as guest. But guest is also not in sudoers.
Using 13.11.1 cldX, because cld has heavy graphic problems with nouveau.
Yes, root passwd was set.
Nice, registered as infinity but comming up as . Can you change this, please.