You need to register with an outside photo hosting site like 'photobucket'
Once you are signed up, there's butten to press to upload photos from your computer to that site.

When they have uploaded to their site, all you need to do is copy and paste the URL onto a reply or thread on this site, from the photobucket site.

Here's a link to photobucket.... Image hosting, free photo sharing & video sharing at Photobucket


And here's a youtube tutorial for photobucket ... YouTube - ‪Tutorial for using photobucket to post pictures‬‏

Hope this helps :-)