How did you sign in as administrator? The Unix/Linux administrator is called
"root" and in Ubuntu the usual way to exercise root privileges is by logging
in as an ordinary user and using sudo at a command prompt (terminal screen).
It will ask you for your password and then grant you unrestricted access to
the system. I think it times out in 15 minutes, but probably only if it has
not been used for that long.

If you need to use some graphical interface utility (nautilus, gedit etc.)
you just type the name preceded by sudo in a terminal screen, type your
password when prompted (it won't show on the screen but works anyway) and it
appears with root privileges.

See what you can do with this information and get back to us if you need
more clarification.