Go to the additional options tab under the reply window and attach them from your computer. I think you have to save them to your computer first.
If you are posting a picture from the interwebs, you can click on the icon right underneath the Italics button. It looks like a picture (context clues are vital). It will give you the following:
Go to the picture you want to post, right click and highlight the url in the 'Properties' section. Paste that url in between the
, and the picture will show up.
It's also likely that you will get the dreaded Red X by using this method. If this happens, you will be ridiculed unmercifully.
Oh, and welcome to The X. Now suck my cock.
It's not about sex, it's about trust.