If an annotation has been saved into a Media Group, you must first open that Media Group, then open the image in the LUNA Workspace or Detail View in order to view the annotation. If the annotation was saved as Private you don't have to open it from a Media Group in order to view it, simply click on it once to bring it into the Detail View or add it to the LUNA Workspace. The same is true if the annotation as saved at a collection level.
If there is an annotation on an image, and you have permission to view it, you'll see the Annotation icon highlighted in green.
Click on the green icon and the annotations will appear. To hide them, simply click on it again.
Being able to share your annotations depends on how you chose to save them:
Privately: If you've chosen to save them as private, you can't share your annotations- if you share a link to an image with an annotation that has been saved as private they will see the image but not the annotation.
To a Media Group: If you've saved annotations into a Media Group that is public, anyone who opens the Media Group and then opens an image from that Media Group to the LUNA Workspace, or the Detail View, will be able to view the annotations. When a Media Group with annotations is copied, the annotations are not copied.
At a collection level: If annotations are saved at the collection level they can be viewed by anyone with access to that collection. When a Media Group with annotations saved at the collection is copied, the annotations are also copied.