Click on the pencil icon along the bottom left of the highlight you want to code.
You can listen to the audio and read the transcript of each highlight as you determine what code to tag the highlight with.
Select the code(s) that most apply to your highlight. Once you are done, click on the bottom left arrow on the highlight box. You will also see your codes displayed on the bottom of each highlight box.
To remove an assigned code, click on the pencil icon on the bottom left of your respective highlight and deselect the code(s) you want to remove.