To add a user, use the useradd command or the adduser command:

sudo useradd -d /home/testuser -m testuser

sudo passwd testuser

“The adduser command is even easier than the useradd command, because it prompts you for each piece of information. I find it slightly funny that there are two virtually identically named commands that do the same thing, but that's linux for you.”

[http://www.howtogeek.com/howto/ubuntu/add-a-user-on-ubuntu-server/]