the short of it is, create a free imagine hosting account (photobucket, etc...) and upload the pics to there. Then insert the URL in between the lower case img tags that this board provides. The FAQ section should have more indepth insight on this.
in other words, you need to be able to post the pictures onto the internet somehow. if you go to photbucket.com, there are most likely instructions there to explain it. then after you get the pic uploaded, it should either give you an address your picture can be found at, or if you just look at the picture, you can use the address in your browser window. i use geocities because it lets you post any kind of file. not just pictures. and i already had a yahoo account from another board. i can also cut and paste the address from there. which im guessing you cant do with photobucket for some reason. once you have the picture posted onto the internet, if you click on the button over the text window you type the messages in here, the one with the little black arrow, and mountain looking thing, that looks like it has a stamp in the upper right corner, it will give you this text.
[ img ][ /img ]
insert your pic url or address in between the 2 opposing brackets. your pic should appear in the message. the button is the one left of the blue #.