If you have the image as a vector file then open it in Fireworks (or ideally Illustrator since Fireworks was really intended for web and interface design), select the shapes and just add a stroke. If you only have a raster version (PNG, JPG etc) then you'll need to use something like Photoshop to add the stroke.
I'd highly advise against adding an outline though, I honestly think it will make the logo worse.