Why can't I add a map to an activity?

Sorry to ask, but are you absolutely sure the map data page isn't already added to your Run activity? If it is, then you won't see the option to add it again.

One way to double-check (other than by scrolling through your pages and looking for the map haha) is is to select Run Settings > Data Screens, scroll to any data screen and press Start, then select Reorder. You will see a list of all the data pages (with either their name or a list of their fields). Press Up and Down to scroll through all the pages and make sure the map isn't there. Press Back and answer No to the Save Changes prompt to cancel the page reordering.

If you're sure the map data page isn't there, you could always try selecting Run Settings > Restore Defaults. This will reset all your settings and data field customizations, so you may want to make a copy of the Run activity first: open the activity list and select Add > Copy Activity > Run. Either that or make a note of the stuff you care about. (One way of doing this is to open the activity settings in the Connect phone app and take screenshots of all the settings and data pages.)

FlowState, I am so embarrassed but grateful! I checked what you suggested and it is already added!! I didn't expect it to look like that, I was trying to set it up so I could navigate a course that I want to complete and not get lost! I think to do that I need to use the "Navigation" then courses settings within the activity? 

Thank you for your time to a very non tech smart beginner trail runner!