A very-often asked question, so it needs a sticky.
You'll need to submit a photo in the "Submission Area" of the Photo Album section of this forum, or have an active account with an ISP or free service such as PhotoBucket, Flikr, Shutterly, etc.
Start up 2 browser tabs (windows), one with the TriumhRat.net forum, where you start a thread or reply that you want a photo in, and a second one with the photo album showing the actual picture.
Click on the desired picture, or select it as required to get it to display maximum size available, then right click and select "properties". Highlight the line with the address info, starting at "http://", then right click the highlight, and select "copy". Note the contents of the properties info, it should end with ".jpg".
Next, switch back to the message screen, type your message, then select the "IMAGE" button below the text input area, then right click in the dialog box and click "paste".
If your free service gives you propietary image links instead of actual .jpg filename extensions, you'll need to use the "URL" button instead of the "IMAGE" button.
All done!
Sample below--
Helpful hint: When uploading images, you should first re-size copies of them to approximately 800 pixels by whatever height your photo works out to at about 300 dpi. This will keep file size and screen loading speed reasonable.
I hope this helps.