That would very much depend on just what software you're herding.
In Flexi it's relatively simple. DO Bitmap->Tranparancy and select the white outside the image. You might have to mess with the tolerance to get it just right. Then select the transparent bitmap and do Effects->Contour Cut and there you are.
In Corel you bring it into Draw, do Edit Bitmap, then in PhotoPaint create a mask of the image, create a new object from that mask, fill the new object with a solid color, like black, and use Save to return both the original object and the new object back to Draw. Trace the mask object and get rid of the mask bitmap. Now you have both the original bitmap and the vector outline of it.
In Adobe or any other graphics software you no doubt do something similar but exactly what those steps might be I can't say.