How to put film in the camera

There is not any in camera developing. This is not a digital camera it is a film camera wherein we put a film cartridge with a specified number of shots into the camera then thread the film leader to the takeup spool, close the camera advance the film a few frames, then we are ready to shoot. After the specified number of shots, 24 or 36, film is rewound into the canister, camera back opened film canister removed then taken to the lab for processing.

You pull down on the clip on the side of the camera. That will open the back of the camera. Pull out a little of the film from the canister. Put the canister into the side with the spindle. Put the end of the film that you pulled out over the roller on the opposite side of the camera then shut the lid and turn on the camera.

One reason may be that the film is not pushed far enough to the receiving spool and the camera thinks it's empty thus rewinding the film.

If this is not the case it needs to be repaired.

You could try removing the batteries so that when it reboots it would be fresh without any memory of an error. However if it continues to show an error it is the camera having a problem.

Am i right in thinking the keystone is a old 8mm movie camera? Never had any experience with movie cameras, or developing their film- I'm goin to assume its like 35mm developing, apologies if this is completly useless advice.
I'm fairly certain you will not be able to develop film in camera (camera will end up pretty wet). If the problem you have is actually getting film out o the camera I'd suggest a changing bag- basically a light tight bag that you put the camera in with your developing tin (if your home developing) or canister if your using a lab, you then have to put your hands inside 2 holes either side and transfer your film from camera to developing container- blind.
I'd advise doing a couple practice runs first with some old unused film just to get the hang of it- it can be tricky.
Again I have no experience with 8mm film processing but I'd imagine the principles are similiar.
You can get hold of changing bags from most photographic retailers, and always follow instructions that came with your film.

Pull up on the rewind knob ( left side ) to open the film door. put film cassette in chamber then lower rewind knob and pull enough film leader to the take up spool. attach film to spool. close the film door then advance the film to #1 on the counter.

It is fairly simple. Insert the film canister with the hole side (not the projection) down. Insert the spool of the camera into this hole and slide the canister inside the chamber. Now pull the film out slightly so that the leader (the narrow portion at the end of the film) aligns with the orange mark at the lower right end of the film chamber. Make sure there is no slack in the film. Close the door and turn on the camera.

you have to pull up on the film rewind knob(pretty hard) and the back of the camera pops open. on the left side is where the film goes attach the piece of film to the film take up spool.

You don't! They're actually built in to the film pack.