First of all, you need to find a host for your photographs. A good, reliable one is
www.photobucket.com. Register an account there, and once you get into your account, it allows you to browse through any photos stored on your computer.
Once the image is uploaded, make a note of the URL and copy it into a post. Put [img]at%20the%20start%20of%20the%20URL%20and[/img] at the end of it. Presto!
An uploaded image
