If using a desktop the photo has to be on the web already. You can link to a photo stored elsewhere on the web, such as Amazon, Google Photos, etc. I upload stuff into a personal album on the site, first, then link to it.
If using the phone app, you can upload photos directly by taking a picture with your phone. It's much easier.
TV: 2016 Ford F-150 RWD Lariat Crew w/ 3.5L EB, MaxTow and tow mirrors.
RV: 2020 Rockwood Mini-Lite 2507S, Propride 3P hitch w/ 1400# spring bars