I only know how to use photobucket but there are others
http://photobucket.com/
http://tutorials.photobucket.com/
http://www.flickr.com/
http://www.imageshack.us/
Upload your image from your computer to the hosting site, then, for instance on photobucket, in 'my album' hover your cursor over your image to reveal a link menu below it ,and copy the IMG code (looks a bit like [IMG]http://something.phobucket.com/albums/something/something.jpg[IMG]) then post that code in your message where you want the image to appear:
hooray!Hopefully someone will explain it better or you will figure it out for yourself
Please keep your images fairly small otherwise they take ages to download and you will annoy people! (you can resize them on photobucket if you use the edit feature)
