How to bookmark
While you're on the chapter you want to bookmark, open the menu on the top right.
Click on the first option(the one with 4 lines) then click which list(to read, read, favorite, and subscribe) to put the chapter/series in. To bookmark a series, do this but be on the chapter list for the series.
Bookmarked series, chapters, and images can be found in Lists in the menu.
If you subscribe a series, you get email notifs when there's an update.