This pin slides in from right to left.  Describing the process with text will be difficult, so bear with me.

Insert the pin into the access hole in the CC switch bracket, then into the hole on the right side of the clutch pedal arm.  Align the slave cylinder input shaft end so that you can the slide the pin into it.  At about the same time as the pin is entering the input shaft end, it will be in far enough such that the enlarged portion of the pin is hitting the CC switch plunger.  DO NOT FORCE THE PIN BEYOND THIS POINT - you would likely damage the switch.  Instead, you must use your third arm and a small screwdriver to depress the switch plunger slightly, then continue inserting the pivot pin, all while keeping the clutch pedal arm and slave cylinder input shaft end correctly aligned.  Keep at it - I used a 5/8" box end wrench to gently tap the end of the pin into place - it will eventually fall into place.

Note: this process would be much easier if the CC switch were removed, but I have notorious luck trying to unsnap plastic retainers without breaking them, so I chose not to remove the switch.

The metal retainer pin slides in from right to left.  If you have difficulty getting the circlip back on, put a very small amount of grease on one face of the clip.  This will make the clip stick to the side of the piston so you don't have to hold it there.  Align it on the pin groove and snap into place with a small screwdriver.  Make sure it is fully seated (and as always, take care to not let this part get away from you during this step).

Installing the lower retainer pin is a bit of a PITA, because the tension in the spring prevents it from lining up easily with the holes in the clutch arm.  It is tempting to stick a screwdriver into the hole on the opposite side and use that to pry the piston into position, but since the pedal arm is made of a composite material I didn't want to risk damaging the hole by prying against it with a screwdriver.  I wound up using a stubby flat-blade screwdriver to pry between the pedal arm and the lower surface of the piston as shown in photo #17.

Enjoy your creak-free clutch pedal!

This pic shows all the parts which I removed during this procedure.

Thoroughly clean all parts you are going to reuse.  Don't forget the main pivot shaft (which is still in the car, attached to the pedal mounting block), or the inside surfaces of the clutch pedal arm where the dowel pins and main bushings sit.

Main bushing reinstalled in clutch pedal arm.  Lubricate both inner and outer surfaces of this bushing with medium coat of lithium grease.

Installing clutch pedal arm on main pivot shaft.  Take your time with this step, and be careful not to break anything.

Reference photo of how the return spring assembly goes together.  Starting from the bottom, you have the bottom half of the piston followed by one circular spring retainer (the two retainers are identical).  Next is the lighter-weight spring and the second circular retainer.  Finally comes the heavier spring and the top half of the piston.

Apply grease to all sliding-contact surfaces of the piston halves, both ends of each spring, and all mating surfaces where the spring ends sit.  Don't forget a light coat on both retainer pins.

This shows the "4" molded into the top piston half.  The bottom half had a "1" molded in this position.  I didn't see any difference, but figured since the old parts came out that way, and the new parts had the same numbers molded on them, why not put it back together the way it came apart?

FWIW, this is what I consider an appropriate amount of grease.

The upper mount is installed, and all the parts have been correctly placed on the upper piston half.

Snap the spring assembly over the lower mount on the clutch pedal arm.

After installing both mounts, ensure the springs are correctly aligned on their spacers.

First step for reinstalling the lower pivot pin.  Carefully pry the piston up until it lines up with the hole in the clutch pedal arm - don't pry it too far or it might pop out of the pocket, forcing you to clean it all off, regrease, and start all over again.

Once you have pivot pin installed through the right side of the pedal, move over to the left side and repeat.

Carefully reinstall the circlip and make sure it is fully seated.

Reference pic of how the return spring should look once it is reinstalled.