The best way I have found is to use an image hosting website. HERE
is a good one. All you need to do is save the image you want to post to your desktop or some other place on your computer where you can find it, then go to the website I just posted. Use the browse button to find the pic you just saved. Then click the Host It button. A screen will pop up which will give you a bunch of codes. One of them will be specifically for posting on message boards like this one. Then all you need to do is copy that code and paste it into a message here and your picture should show up once you post the message. If you still have trouble then let me know and I will try to walk you through it better.