The diary shows the events in order of user and date and time. You can edit which users appear in the diary (providing they have diary settings enabled - please set these by following these instructions)
You can add users to the diary if you want to see their event, you can remove users if they are on holiday/no longer use the diary for example.
How to filter users in the diary:
Click into your diary from the navigation bar.
On the right of the screen, you will see some options
Click 'Users', this will open a list of the users you have. You can add a user to the diary by ticking the box next to their picture. You can remove the user from the diary by un-ticking this box. You can reorder users in the diary by clicking and dragging the names in the list. Click 'Save' when you are happy with the users you can see in the diary.