How are you exporting? If you want a working button dirextly from FW with no other coding then export as HTML and images then in Dreamweaver Insert>Image objects>Fireworks HTML
BUT the better way is to make the button with rollovers (images will be placed in frames) export images, be sure current frame only is not checked and export. In Dreamweaver insert button then use the swap image behavior for the rollover. When you exported from Fireworks the rollover image is appended with the number 2.