Threading an 8mm film projector is not as intimidating as it may seem. There is really only one way the film will flow through the machine, so you really can't mess things up too badly. In fact, you will find that 8mm film is easy to handle and load. By following just a few simple steps, you'll be watching your 8mm home movies in no time.
Place the reel of 8mm film on the front mount of the projector. This is where your film will be unraveling from as it travels through the projector. Place the empty reel, hereafter referred to as a take-up reel due to the fact that it "takes up" your film as it comes out the other end of the machine, on the rear mount of the projector.
Find a small button near the top of the projector and press it. This will open what is called the "roller arm," which allows you to feed film through the projector. This must be opened. If it is not, you'll be able to tell as you won't be able to get any film into the machine.
Feed the beginning of your reel of film through the small entryway in the front of the projector right above the lens. This is called the "feed hole." As you are doing this, be mindful of the tiny holes on either side of your film, called "sprocket holes." If your film has sprocket holes on both sides of the film, you can load it into the projector any way and not damage anything. If your film has sprocket holes on only one side of the film, when loaded into the projector they have to be on the inside of the projector as opposed to on the side that is the closest to you. If you load the film wrong at this point, you run the risk of the projector tearing holes through your film.
Pull a little extra film off the front reel as you begin to feed it through the projector. Be sure to give yourself a little bit of slack. You don't want the film to be too tight at this point. Run the film through the feed hole and through the inside of the projector. There is only one very clear path it needs to follow - down from the feed hole, behind the lens (more specifically in between the lens and the projector lamp), down around the bottom of the projector and out the other end.
Attach the tail end of your film to the take up reel, either by putting it through a slit in the reel or by taping it. Once this is done, you can close the roller arm. This will make sure the film is secure inside the projector.
Turn the knob near the front of the projector once to start the motor which runs the film, and once more to turn the lamp on and project the film. You can focus as necessary by twisting the focus ring around the lens. When your film is done you can let it run off the front reel and all the way through the projector until it is all on the take up reel.