When you Subscribe to Calendar via
Outlook the new calendar may be displayed as a
separate calendar. Making the new calendar
display in your primary calendar is
easy!
1. In the navigation pane the new
calendar is added. Be sure the new
calendar box is checked.
2. The new calendar displays next to the calendar that already appears. On the new calendar tab, click arrow, View in Overlay Mode.
3. The calendars are now in overlay mode, displaying all events in one calendar!
Here is a link to Microsoft support instructions for View multiple calendars at the same time. Scroll down to "Overlay the calendars".