To annotate a redaction: 

1. Select the annotation tool at the top of the page.

2. Click on the redaction you would like to annotate to bring up the annotation menu on the right-hand side of the page

3. Either select a pre-defined annotation from the list or enter your own comment using the text box. Hit return / enter to apply the annotation

]You can drag the annotation anywhere on the page and add as many as required