How to Add image in the region pop-up?

Hi,

How do I add an image inside the pop-up which opens when you click on a region
as shown on this screenshot ?

When I click in “Image url” text field down the “detailed settings” tab, the list of images appear, but when I click on “insert inside article” button under the chose picture, no address appear in the”Image url” text field.

And if I paste an image adress in this fild and click on the refresh button, the address disappears from the field and the image doesn’t display in the map region pop-up.

Please help. ??