In case people are confused (I've seen it), the picture has to already be on the web first.
Some website has to host the picture (flikr, or whatever).
The forum just gets the image from another website (like looking up a page then displaying a thumbnail, if that helps).
So, if you want to post a picture from your computer you need to find a site to host it first. Then do the steps described above. (Note: when posting you'll see a bunch of buttons "B i u Quote img URL" the "img" button is what will tag the website as an image and cause it to display properly on RealJock. Most forums will have something similar.
(rnch: And it's not hard. It's super simple, it just sounds complex when you mention every single step. Instructions for how to make a peanut butter & jelly sandwich sound hard too if you write them all out. [First find two cans, one of peanut butter, one of jelly. Almond butter is okay too, as are various jams, but make sure they're fruit. First search for an expiration date on each jar, which may be printed in various formats including ... ])