1. Click on the design canvas and start typing
This way you will create a pinpoint annotation.
2. Click & drag over the design canvas and start typing
This way you will highlight an area which you're talking about.
TIP: If you decide to start over - for example, select a different point - just hit ESCAPE before you Post the annotation.
NOTE: The annotations are always tied to a design version. This means, that when you add a new design version with a different layout, the older annotations will be still positioned as they were before. The new design version should respond to feedback from the previous design version annotations. When the suggested changes are implemented, you can either solve or delete the old annotations.