Log into the main site and then go to the members Area. The click on the Members Gallery link, which can be found along the top row of navigation, and also under the left hand profile menu.
Once the gallery window loads, click on "Upload file", which can be found at the top of the page in the row of links. This will load the Upload file screen. Click on the Brose link next to the first File Uploads entry and select the image you wish to upload, and then click continue, and the site will upload the image. Once uploaded the next screen will allow you to select the album it is to go into, in this case this is the "Slamtilt - Ace of Space" album, and then give it a name, which for competitions will be the hiscore and you username, a description if you wish, and then click continue to add it.
Then to add the image to the forum, navigate to the image in the gallery and open it up at full size so it appears in the popup window, then right click the image and either look at the image properties and copy the image location, or select "copy image location" if you are using firefox, and then just use this url in the forum to add the image.
As I mentioned in the other post, the next version of vBulletin has a built in members gallery, so we won't have to use coppermine for much longer, and it will make life much easier.