If the latter, you must find a place that you can upload the photo to, such as photobucket (Although I hear that they are not very escort friendly these days.)

Once you do have it on the internet, open the photo and the picture's URL will be up on the address bar.  Highlight that address and then right click and hit copy.  Then go to the address box when you post on TER and click on that, then right click and hit paste.  The URL will now be added to your ad.