If you allready have your pictures on photobucket, choose which one you want to post. Highlight the top line under the picture (Url, click on it to highlight it. Right click on it to copy, go to your post that you are doing. Up in the top of the message area the 7th item over from the left (insert image), click on that, a box will open up in the top of the screen. Right click and paste what you copied from Photobucket.
Just make sure you don't have two http"s in the line.