Let me know if this doesn't answer your question. I realize it's hard to explain details on Twitter. Feel free to comment or ask more questions here.
Using a snapshot of the the Glip Twitter page as an example below, I've posted this to a conversation in the Glip program. When you click on the image it will zoom in and give you are larger view of the image where you can add annotations. Simply click anywhere on the image, type a comment in the box like shown below, and hit the "enter" key.
Notice the small green marker. When you mouse over the image and click on the marker, you'll be able to see the previous comments and add more comments.
Just letting you all know we release a new version of Glip for Android last night. You'll want to update your app as this new version performs much better! Be sure to eave a review in the Google play store and let us know what you think.