If you're asking about how to modify an image from within Access itself I've never heard of such a thing and would be of no help.
If you're dealing with images, you should be using an image control, not a bound object control.
If your form has multiple records or single record view with navigation controls, then the typical approach is to "load" an image into the image control, getting its path from a table. Thus when you get to the record that pertains to me, that record has a field with a path to an image of a very small dot
The current event of the form tells the image control where the picture is that should be displayed. If you want a default image, then such code needs to basically say, "if there's no image path for a record, the image control should show 'defaultImage' instead.
Might be kind of difficult for your level given your proclamation about not knowing code, especially since you seem to want to launch the default app for an image type (double click event on the image control would suffice) but definitely doable. If you have time to research, start with how to use an image control. Most of the other details should fall into place as you find different sources showing various ways of using them. The biggest take away I think, is to not store images in tables and load them into a bound object frame. Storing files in tables will rapidly cause db bloat if not accelerate you down the path of db corruption.
The more we hear silence, the more we begin to think about our value in this universe.
Paraphrase of Professor Brian Cox.