Mac or PC should not make a difference... First off for this forum you can not directly upload your images to the site. You have to find a host or server for your images that you can link to. Try searching this forum for image hosting or hosting. I think this might have some free services. http://www.boltcity.net/forum/viewtopic.php?t=1166
Once you have your images on the web then all you have to do is put the URL of your image inbetween the [img]and[/img] tags in your post. The URL itself is an address for your image like http://www.google.com/
exept in your case it would be more like http://www.yoursite.com/image.jpg
. Good luck.