You can create any number of groups through which to categorise your users. This enables you to separate your users and diary events according to these groups. If, for example, you have users spread across the country, you can set up user groups that are location specific in order to see on the diary only events that are related to that particular group.
If you do not have any user groups set up yet, you can do this easily through your system settings. Scroll down to 'Users' and select 'User groups'.
From here, you can create your user groups. Give them a name and then click 'Add user group' to create them. You can edit the titles later if need be.
Once you've got the groups you need, you can add users. To do this, go to your company settings and click into 'Users'. This will give you a list of your current system users. Click 'view' to bring up their individual profiles and then 'Edit business details'.
You can now select the appropriate user group from the dropdown menu. Make sure to hit 'Save' after making any changes to this page.