In Dreamweaver, open the Preferences panel and choose File Types/Editors. Under Extensions, make sure that .png is highlighted. Click on the Browse button in the Fireworks box. Browse to the Fireworks app icon, click on it to select it, and then choose Open. The browse panel will close and you should see Fireworks listed under Editors. Highlight the Fireworks line in the Editors panel and then click on the Make Primary button. If this doesn't work the first time, remove any other image editors you see available and repeat the same steps to make FW the primary image editor for DW.
Hi Linda, many thanks, I had to remove and than re-add it and now it works.