Adding a Favorite:
While you are on the page for a topic you are interested in, tapping on the star at the top right of the screen will add this to your favorites. When you add a favorite, the star will turn solid.
Removing a Favorite:
To remove a favorite, select the topic you wish to remove from your favorites list. Tap the star icon at the top right to remove the category from your favorites list. When you remove a favorite, the star will change from solid to an outline.