You need to have the image hosted on-line somewhere (eg Flickr, Photobucket, or your own website) and embed the URL between the UBB image tags, so assuming you want to post the image '1.jpg' and it is hosted at www . somewebsite . com / images, your post would look like this: [img ]http://www . somewebsite . com / images /1.jpg[/img ] (Note: Delete the spaces between the characters, they're only there so that the system won't actually try and interpret this as an image post)
Or subscribe to The Photo Forum which will unlock the uploads feature, the hidden meeting grounds (subscribers forum section) and give you a snazzy green line above your avatar.
