Kim use a free online picture hosting site like photobucket, putfile, yahoo, google. Once you have uploaded to one of those free picture hosting sites your pic will give you a web address for the picture to clip and paste here. On the menu bar on the forums you will see a green tree icon that looks like a picture. Hit that button and it will ask you for a link address of your picture so just paste the link or address of your picture in there and it will show up on the forums. Try to reduce your pics to 800x600 for the forums when it asks you what size do you want.
If you go to google and type in free picture hosting web sites you will get hundreds of free sites.