What is the ultimate destination for the "picture"?
If it is going into a PowerPoint or Word document you can use the Drawing
toolbar in those applications to create an arrow and then move it, resize
it, color it, etc. to point to various locations on the final product. When
I am using a detailed picture in a PowerPoint show and I need to identify
parts this is how I do it. That way you can use Custom Animation in PPT to
have the arrows show and then disappear when needed during the presentation.
To turn on the drawing toolbar in either program, right click on the toolbar
at the top and then select Drawing. It will appear at the bottom of the
program.