Hi Patty and excellent question!
I suspect that you have the “Default Page Template” as your template settings on the same screen. Is this correct? If so, that’s the reason that the content you entered would show on the single event (which uses the plugin’s template) but not the main calendar (which is set to the theme’s page template).
You can set this back to “Default Event Template” to get the text in there.
Another way to go about it is with a function–perhaps in your theme’s functions.php file or as a standalone plugin. Here’s an example of what that might look like. Note that you can also change tribe_events_before_html to tribe_events_before_template and that might have the same effect.
Let me know if that does the trick. 🙂
Geoff