Hi Sue,
Are you asking if they show up on the dashboard like in the image attached? This number is calculated by adding activities that are not cancelled or completed and that have a DueDateStart that is less than or equal to the current date.
If your email preferences are set up correctly you can edit your user settings by going to Customize>Users to set up activity reminders.
I also suggest you watch our webinar on activities in the Method 2.0 section of this link. Let me know if you have any more questions!
- Jason