If you would like to have a photo of yourself appear to the left of your messages (and later on your threaded emails), click on "Forum Photo" at the top of the Forum page (or on "Edit/Upload Photos" on the left navigation panel).

If the picture that you want to use is already uploaded to your profile page, just click "Make This My Master Photo". If your photo is not already there, you will need to upload it (see "Upload Photos to Profile" under the "Using Our Site" category).