Sign in to ** to update application for that account
these are sort of "nuke from orbit" directions; there's likely a less extreme way, but this should work:


shutdown
boot to single-user mode by holding down ⌘ command-s on boot
enter these commands at the console

fsck -fy
mount -uw /
rm /var/db/.AppleSetupDone
shutdown -r now

run through the Setup Assistant creating a new administrator account