To make sure you have the buttons mentioned by James:
1) Click on Settings
(top right of the home page after you log in)
2) Click on General Settings
(mid-way down the left side of the page)
3) Scroll to the Miscellaneous Settings
section at the bottom of the page and change the Message Editor Interface
from Basic to Standard
. If you want even more editing options, choose Enhanced
Also, you images MUST be hosted elsewhere. Sign up for a free account on Photobucket.com or similar free hosting site. Once your images are uploaded there (no bigger than 1200 pixels, please) then just copy the URL for that hosted image and paste in in the thread with the hot button noted above.
to the end of it without using the hot button. It does the same thing.
if I just post the URL to an image, it will look like this:
But if I add the HTML code
after that URL, it displays the image like this: