Step two
Drop in a json-camera file. It comes back as the photograph it started as, under the filename it went in with. The right model is picked automatically by matching the fingerprint stored in the file.
Leave this on automatic unless you know better. The file records which checkpoint made it, and decoding with any other one is refused rather than quietly handed back as noise.
Only files made by this site will open. The model weights are part of the format, so a file made with a checkpoint this server does not hold cannot be rebuilt by anything.