Pictures are not supposed to be links or directly from your PC.
First, the picture needs to be uploaded to a web host; like photobucket, flicker, or even a locked folder on facebook (like I do). Then after it is uploaded; you view the picture online, right click, and select "copy image location". At this point you come back to the forum and select the third icon from the right; the one that says "image" when you hover over it, and paste your image location into the box in the popup, then click "ok". Then the picture will be shown like this: