Select any text. On a phone, press and hold, then drag the handles over what you want.
A small bar appears: ✦ Highlight, Tag…, Ask, Share.
Tap ✦ Highlight and it is marked. Marks cost nothing.
Tags
Tag… marks it with one of four labels instead: Exam, Confused, Memorise, TMA.
Use them. They are what lets you come back later and revise only the parts you found hard — see below.
To change one afterwards, tap the mark and choose Add tag or Change tag.
Notes
Tap a mark and choose Add a note to write something against it. After that it says Edit note.
Finding your marks
Tap the bookmark in the bar at the top of the reader. You get everything you have marked in this course, and tapping one takes you back to it in the book.
Your most recent marks across every course are on your home page, under Recent marks.
Revising from them
This is what tags are for. Once you have marked things, the Ask panel offers Everything I marked and one choice per tag — Tagged Confused, Tagged Exam, and so on.
Asking against those gets you an answer about exactly the parts you struggled with, and costs the same as a passage question. See Ask a question about what you are reading.
Removing one
Tap the mark and choose Remove.
They follow you
Marks live on your account, not on one phone. Mark something on the bus and it is on your laptop that evening. They stay if you remove the course and add it back.