Hover over PEOPLE in the navigation and click ADD. Enter the users necessary details (minimum required details are an email address and password) and click Submit.
To edit a users details click on 'PEOPLE' in the navigation, then click on the pencil icon to the left of the Person's name in the list. When editing a users information be sure to click SUBMIT to save any information entered.
When viewing the People list, you can use the search filters to help find them.