Loading the Bolex:
Parenthetical notes refer to the parts labeled in Controls on the Bolex
Before shooting the diopter should be set. The instructions for doing so follow:
First rotate the turret so that there is no lens in front of the gate. It is easier to set the diopter without an image to distract you. An alternative way is to use a telephoto lens racked way out of focus with the aperture wide open.
The locking ring is now loosened by turning it counter-clockwise. This is the slotted ring, closer to the rubber eyecup.
Now the adjustment ring can be turned while looking through the camera. This ring is the one with the little screw mounted on the side and a white scribed line that can be moved up and down a scale with a "+" and "-." While looking through the camera you will see different planes within the viewfinder come into focus as the diopter is adjusted. The groundglass is located the same distance from the lens as the film plane. The groundglass is etched with a field of grain, so when the grainy pattern is at its sharpest the diopter is set.
Feel free to take your time doing this. It can be easier to see the grainy pattern if the camera is pointed at a light source or bright subject. There is often dust visible in the viewfinder. This is not something to worry about, because it isn't seen by the film. In fact, bits of dust on the groundglass can often help in focusing the diopter.
Once the grain of the groundglass is visible the diopter can be locked by turning the locking ring clockwise.
The next step after the diopter is set is to wind the camera's spring. This is because the automatic threading mechanism in the Bolex works by running the film through the camera, and the camera won't run if it isn't wound. The spring is wound by turning the winding crank (right side-c) counter clockwise.
The diopter set and the camera is wound, the next step is to open the camera door. 
On some doors the latch is labeled "O" and "F." "O" is open ("ouvert").
There should be an empty spool in the camera (if there isn't you might be in trouble). 
The empty spool should be taken out, you can use the spool ejector for this (left side-g). 
The spool of unexposed film is then put on the top spindle, the supply spindle (left side-a) so that the film comes off it from the bottom in a clockwise direction.
Now the film needs to be cut using the film cutter (left side-e) to allow it to run smoothly through the camera. 
The film is inserted between the two blades of the film cutter and the top blade pressed down. It is important to make sure that the bit of film that is cut away doesn't stay in the camera where it could get caught on something and put a scratch on the film.
The loop formers (left side-c) must be in the closed position, or else the camera will jam in the loading process. They can be closed by turning the loop former lever (left side-d) downwards. 
Now the film is pushed under the top sprocketed roller, while at the same time the run button is hit (right side-a). 
The as the camera runs film should pass through the loop formers and out from over the lower sprocketed roller.
Sometimes the sprocketed roller doesn't catch onto the film's perforations and the film needs to be pushed or jiggled to engage with the sprockets.
The camera should be run to let about two feet of film come out. 
The end of the film is then pushed into the slot in the center hub of the empty daylight spool and the film rapped around the hub clockwise, with the emulsion in, until it will fit onto the take-up spindle (left side-b) with the minimum excess. Rapping the film around the hub of the daylight spool causes it to tighten around itself, but it is worth checking that the film hasn't slipped out of the slot by trying to turn the take-up spool clockwise once it is mounted on the hub and making sure it offers resistance.
One thing to be careful of is that in the process of putting the take-up spool in place the film hasn't gotten caught on either the spool ejector (left side-g) or the little device just below it (designed to push the film onto the take-up spool in case the spool is bent). If the film is going over rather than under either of these on its way to the take-up spool it will cause a scratch on the film and possibly cause the camera to jam.
Another thing it is very important to check is the pressure plate (left side-f). 
All it needs is a gentle push in the direction of the front of the camera to make sure it is engaged. It will appear much the same either in the engaged or disengaged positions. If it clicks into place when it is pushed then it was not engaged, but is now.
When the camera door is put back into place it pushes the loop former release button on the loop former lever, and the loop formers spring open. If you are the sort of person who puts more faith in what is seen first hand, then you can push the loop former release button yourself and the loop formers will spring open. 
If further assurance is needed, then the camera can be run for a "burst" (a second or less) to see that everything is functioning properly. If you had a lot of trouble threading the camera, this extra test is a good idea to make sure the loops are ok.
[Note: If you are using an older Bolex with a loop former lever that doesn't have a center button (left side-d) the loops are not automatically opened when the camera door is put into place. The loop former lever must be moved to the up position so that it faces out straight to the left.]
The camera door can now be put back on. If it doesn't seem to want to go on the first thing to check is that the door's latch isn't on the "F" setting, which is the closed setting (fermer). The latch must be set to "O" to go back on. 
The door needs gentle pressure applied to it to make sure the catches engage properly when the latch is turned to the "F" setting. If the door doesn't seen to want to go on it is a good idea to check that the pressure plate is engaged. The silver knob at the top of the pressure plate fits into a recess in the door and supposedly the door won't go back on if the pressure plate isn't engaged, but unfortunately this isn't always the case.
With the door in place the camera can now be turned over with the right side facing you and the film advanced past the flares by running the camera unto the footage counter (right side-d) has moved from "ft" to "0," unless of course the first image is meant to emerge out of the flares.
The spring can be wound again and shooting can now begin.