First, edit the story. Move your mouse over the upper-right-hand corner of your story. You'll see a little gear-like icon. Click on it and you'll get a drop-down menu. Choose "edit." Sreen-shot below:
Secondly, choose "Full HTML" on the toggle-menu beneath your chosen story.* The point is that file browsing may not be enabled for "Filtered HTML" -- you'll have to experiment. Screen-shot below:
3. Click in the approximate area to which you would like to add an image. (You can move it (adjust it) later.)
4. Next, click on the photo icon and browse for your image.
5. Select your chosen image by clicking on it one time.
6. Give it a description in the "alt" or "alternative description" field, and, then, click "OK." Sreen-shot below:
7. Finally, scroll down and click "Save." Don't forget, now. ;-)
* This will vary from one Web site to another depending on how its creator configured the editor, in most cases Ckeditor and IMCE for file browsing.