just above the top left of the photo you want to link are several "buttons"
facebook/twitter/google+ etc ect....
the last one looks like a chain link.... left click it ..... a drop down window will appear

copy the IMAGE CODES(for forums and boards)

Paste that directly to the reply to post window you have when your doing a post....



it will produce a smaller photo in your thread (as above) but allows a faster thread upload for those viewing the thread,
should they want to see a larger version then they simply have to left click on the photo and that will take them automatically to the site and the larger version of the photo.

Once you are ready to 'submit' the thread click the PreviewPost button first and view the post for a check on how it will look

The main advantages of the smaller pic are .....
it keeps the bandwidth down so this keeps the forum/board fast in its loading of the pages....
it stops the expanded window look with typing going off into the righthand side never never region and having to use the bottom slide to "see" all of the post because the typing field now runs the full width of the photo.....
and you can monitor how many people are actually viewing your stuff, from this you learn what people generally want to see more of