You need to host your images somewhere, then when you have the image online place the link to it it between [IMG][/IMG] tags.
IE: this is the link to your image:
http://www.msportster.co.uk/data/p_paint001.jpg
Place in tags:
[IMG]http://www.msportster.co.uk/data/p_paint001.jpg
[/IMG]
And then you get:
I believe
http://photobucket.com/ is a free image hosting service
If you want the image to be clickable combine it with a link:
[URL="http://www.msportster.co.uk/detail.asp?cat=29"][IMG]http://www.msportster.co.uk/data/p_paint001.jpg
[/IMG][/URL]
Then you get: