In the top-left corner of the calendar (just to the left of "Monday" if you're viewing the entire month), there are two thin, gray, vertical lines. Click those lines and it will open a menu for you to select all of the activities, goals, workouts, etc., that you'd like to display in the calendar. Be sure to click the box next to "Running" or whatever activity you're trying to display because it looks like those boxes are unchecked by default.
