Images are not an option when posting. You can link to an image, but it won't display on the forums.
This is asked and answered all the time in the Website Questions and Suggestions, and should also tell you in the FAQ and or your User CP that the option is turned off. Or wait, at the bottom of every page it tells you forum rules, [IMG] code is off.
Also in the future, questions regarding the Website belong in the WQ & S where this is being moved to now.