One one window and go to photobucket. Upload your photo.
Select that photo and a box will appear called Share Links. Go down four boxes and click on the IMG box. It will say copied.
Open another window and go to the forum. Open a new thread and paste. The IMG file of your photo will now be pasted into the post.
That's how i got this image inserted here. Once you insert it, you do not need to do anything else.
For flickr, I have to save a photo (using the arrow pointing down at the line tool) to my desktop....upload it to photobucket and proceed as above.
Post on.