When you open My Trackers, you’ll see a list of available trackers. Tap a tracker for details about how it functions and what information it tracks. If you’d like to use that one, there’s a Subscribe button that will activate it for you. Once you’ve subscribed to a tracker, you can use that tracker’s button at the bottom of the window to open the data fields.
On the Tracker window, you’ll see a series of data fields. Tap the Add button in the top-right corner to open data-entry window. Enter the requested values and tap the Add button to enter that data. The fields will populate the fields with your entered values.