If they dont have a Facebook icon you can use, and your on your computer, you have to save the picture to your computer first, then upload it from your picture library to Facebook. If your on your phone/iPod you basically do the same thing but save the picture to your phone/iPod.
To transfer photos from Photobucket to Facebook, click photo or folder of photos you want to transfer. At the top "share", click on the Facebook icon then sign into your Facebook account. Then click share on Facebook.