Once you've uploaded your picture to the gallery, find it in the gallery, double click on the picture
You will see (down below your picture under PHOTO DETAILS) the following:
Linked thumbnail: url-http......
Linked image: url-http//www......
HTML code: img s/c = http.....
highlight the everything in the second box (under Linked image) right click your mouse and hit copy
click on forum
go to the thread you want
click on reply
right click your mouse and hit paste - VOILA your LO will be posted.
You can type before or after you hit paste.
The other trick I learned was that before uploading to the gallery, I saved my LO's by hitting file, publish, publish to images - this saves it in a smaller format, as you will notice my LO's get posted in the thread at a smaller size than some of yours.. it's because I've become a clusting maniac and my LO's are sometimes too big to post.. by doing it this way, you'll never run into that problem.
Hope this helps