From your home screen, select [My Details] from the menu down the left

Select from the Tabs at the top of the screen 'Users'
All current users will be listed.
To add a new user, use the button [Add User]
Complete all the fields, those that are mandatory are marked with an asterisk, then choose [Save]

When done, choose the button [Send SignUp Link] which will send an email to that user to create their own password.