The very first thing that you must do is to get your self a FREE photobucket account.
Trot on over to Photobucket http://photobucket.com/ and register for your new account.
Now that you are registered and logged in to your photobucket account we need to upload some images from your computer..
I'm not going to explain as I feel it is better to see what is done rather than me trying to explain here.
Here is a link to a youtube Video showing what is needed to get an image onto a forum.
http://www.youtube.com/watch?v=jehxvujkalM