If you have an existing photo account somewhere like Photobucket, Picasa or Flickr, you can link to those, the album must be set for public view. When you're creating a new thread, you'll see an icon that looks like a picture frame with a tree in the middle (insert image icon). Just click on that icon, and copy the image URL and paste the URL in the blank.
You can also create an album here at CSP. Up at the top where it says Community, pull down and you'll see My Albums.
• Click create new album (set for public view)
• Add photos (400 x 600 pixels should be OK)
• Copy the BB code at the lower right and paste that directly into your new message.
• Preview your message to see if it linked OK
If your preview doesn't come up, you'll need to try it again. Common mistakes include an extra "http://" at the front of your link. The other one is linking to an album not set for public view.
Things to avoid: Large image files 1MB and up (you'll piss off all the dial up members, there are a few) and thumbnails, which are too small for anyone to see.
If you get stuck you can ask here and someone should be able to help you out.