At the end of a text, a useful way to annotate is to
rewrite the section in your own handwriting
make a list of the key points
write the initial introduction to your own essay
make a list of the words that you are most familiar with

At the end of a text, a useful way to annotate is to make a list of the key points.
Annotation refers to some notes at the end of the text - so if you want to annotate your study properly, you should just jot down some of the things that you want to explain or comments that you may have regarding the text you've just written.