Desktops may have applications to create a user. Plasma has for an example such a graphical application.

However we do not need a graphical user interface (gui). You can always create a new user and give him/her a password via the terminal.

You can find the relevant and up-to-date information on the Arch Linux page phase 2. 

Above link and page is improved constantly.

You only need the line of

useradd

and

password

Do not forget to add sudo in the front of your command.

Then you log out and log back in with the new user account.