Not finished, one of my cats came to see me and erased the 2nd part! After clicking copy, go to the USMB page you want to type on, left click the message box so you get the hash mark that shows you where the message will start, RIGHT click the mouse, should see another separate frame open up and look for PASTE, move cursor over PASTE left click, and your picture should magically appear! If it doesn't work, ask your IT guy to show you!
OK, try this and see if it works for you. Open one window with the picture you want from the internet. Next open another window with the USMB website on it. Go to any topic on USMB, and go post a new message, or whatever they call it. Once there, go back to the picture on the net you want, put your cursor over that picture, RIGHT click the mouse and you should see a separate frame open up with things like open link, print target etc. LOOK for the word COPY, move your cursor from the picture to that frame and left click COPY.