The quickest way to do this is to use choose the "+" sign in the Filters section of the Properties panel, then scroll down the list to Photoshop Live Effects and select the Stroke effect. It's one of the few actually useful PS Live Effects within Fireworks, because Fireworks has no way to natively add a stroke to a bitmap.
A few ideas:
- For a very simple border, use Photoshop Live Effects and choose the Stroke option. (Photoshop Live Effects can be found at the bottom of the Filters/Effects list in the Properties Inspector, once the bitmap is selected.)
- Another simple border could be created using a Glow effect. Set Softness to 0. (Like the Photoshop Live Effect, this can be applied from the Properties Inspector, once the bitmap is selected. Look under 'Shadow and Glow 'within the Filters/Effects list.)
- For more control over stroke style, create a rectangle to match the contour of your bitmap. Set the fill to None. You can use the Properties Inspector to help match the width and height of the rectangle to that of the bitmap, and use the Roundness slider to adjust the rectangle's corners.
- As a variation on the above idea, you could use a vector to mask the bitmap—this would be a particularly good approach if your bitmap did not already have rounded corners. Create a rounded rectangle as described above, setting the fill to either None or white. Then select both the rectangle and the bitmap together and choose Modify > Mask > Group As Mask. Once the mask is applied, select its thumbnail in the Layers panel, and you'll be able to adjust its appearance in the Properties Inspector. You'd want to choose "Path Outline" and "Show Fill and Stroke" in order to have the desired stroke appear.
(Whoops! Looks like Jim and I cross-posted...)