Make dopus viewer windows default for images

Is there anyway to make the the Directory Opus viewer default for viewing all supported image file types?

If I double-click an image in dopus it opens in the viewer ok but if I try and open an image in Firefox for instance it defaults to "TWINUI (default)" which is the Windows viewer. I can select other and it gives me a list of other applications to use but the dopus viewer is not listed.

Thanks

From the FAQs: HOW TO: Use the Opus image viewer inside or outside of Opus

Thank you for the quick reply....it worked.