Add a regular user in Kali Linux

Create a new user, say timus.

# adduser timus

Add user to sudoers group. This enables the user to become root when needed, for example to install new software.

# usermod -a -G sudo timus

References:
http://8thstring.blogspot.com/2013/07/howto-create-new-user-in-lubuntu.html
http://8thstring.blogspot.com/2012/12/adding-existing-user-to-group-in-ubuntu.html