If you are still stuck then you need to host your pictures on the web i.e. flickr, Photobucket, etc. Once that is done you need to right click on the pic you want on STW & copy the URL. On your STW Reply click on "IMG" then paste the URL in the box this will put the URL inside the correct tags.
[ img]http://farm4.static.flickr.com/3263/3172973945_217f624705_o.jpg[/img ]
without the spaces after the first & before the last bracket will give you
So come on show us yer bike then!!!!