To add a single user to the system:

1. In the Control Panel, click Users and groups, Users.
   
   
2. On the Users page, click Add. 
   
   
3. On the Add user page, fill in the relevant fields such as Username and Title. Click Save when you're finished.
   
4. To assign a user/s to a group, go to the Users page. Select the user you want to add to a group and under Actions, select Add to group. To add users in bulk, tick the first box on the grid.
   
5. Type the name of your preferred group in the search bar and click the "Add" button. Once selected, click Add to group.

Adding a user to a group defines what sort of access rights that the user has. You can add a user to more than one group.