Here is how we can manage users in Ubuntu terminal:
It is very easy to add a user under linux terminal (we use the standard Ubuntu LTS Gnome terminal here), just run
sudo adduser usernamehere
and enter some password for the user being created. Add some additional information if needed (names, occupation etc). This step is not necessary and to skip it just hit Enter.
Now when the user is created, one can log on into that user profile by entering
su usernamehere
And of course, to log on to that profile user has to enter the correct user’s password!