I go to manage attachments, found just below the submit reply button...then I click on files with pictures...when I find the picture I want I double click on it. It will say upload.. double click on that button..
it will upload the picture as long as it is below the size indicated...too large and it will spit it out and refuse to upload it.
Hope this helps. There is a way on photo bucket but I am not familiar with that one very much.