In order to access features such as
- adding/editing instruction and transition comments
- setting a pose to "mirror" (for right and left positions)
- delete a pose from the canvas
- copying/posting poses
...you need to hover over the pose image and right click.
A menu will load with these options.
Now, if you are a Mac user, you will not have a right click on your mouse. So, to emulate this, simply press and hold the Ctrl key and then click your mouse key at the same time the Ctrl key is pressed down.