To navigate, use the app's interface elements.
On subject pages, click either side of the page to go to the next or previous subject.
Click the menu's Search button to open the search panel.
Click the search panel's left and right arrows to go to different search sections.
Check encountered subjects, or bookmark a subject. Keep track of encountered and bookmarked subjects under the search panel.
Open the search panel from the menu, then use the search panel's left and right arrows to go the proper section.