The Dashboard is the landing page in myHealth Hub when you first log in, and displays your data Widgets, which are data types, such as Oxygen Saturation. The data in each widget is displayed in chart format, by time period selected (tap on your selection).
When you log in, the Dashboard icon is located at the bottom left of the page, and looks like four small blue boxes. If you navigate to somewhere else in the app, when the Dashboard icon is tapped, you will return to the Dashboard page.
On the Dashboard, you can change the data view from chart view to a List View by tapping the widget's List icon at top right -- the icon looks like three horizontal lines. From the List View, tap the arrow at top left to return to chart view.