create user ubuntu command line
sudo adduser USERNAME
# choose password
# other fields can be left empty
sudo usermod -aG sudo USERNAME
# change user to check if everything is ok
su - USERNAME
whoami
# output > USERNAME
sudo whoami
# output > root or an error
# if error switch back to the other account
# and do the following to modify /etc/sudoers
sudo visudo
# find a line like "root ALL=(ALL:ALL) ALL" (or similar)
# add an identical line for USERNAME, like
# "USERNAME ALL=(ALL:ALL) ALL"
Ctrl+O, Ctrl+X # save and exit
# change user to check if everything is ok