It is actually quite easy. I use cases and reloading equipment from
H & C Collection in France, but they can also be obtained from Dixie.
1. To prime the case, insert a #11 or 10 percussion cap in the bottom of the shell with a primer seating tool that comes with the reloading kit. Like original pinfire cases, the H & C cases have a recess in the bottom of the case into which the cap is inserted. The firing pin should hit the inside or the cap, so make sure you insert he cap 'upside down' facing the hole for the pin. You can see a picture of the tools in
my black powder book or at the H&C Collection homepage.
Here is a drawing showing the concept of the primer and pin:
2. The firing pin is inserted through the hole at the base of the case and into the cup of the cap. It should be a tight fit, so use a pair of pliers or similar to seat the pin. The pin should stop about 1mm (.04") from the priming compound. Since the pin now is inside the cup it efficiently locks the primer into the recess. Proceed with caution, because one blow to the pin may now set off the cartridge. Some shooters use glue or Loctite to secure the pin.
3. Next, fill the case with powder and seat a bullet on top. Finding a proper bullet heel base bullet may be challenging, but roundballs work well. As you can see on the picture above the cartridges is loaded without a crimp since the case walls are thick and hold the bullets easily, but H & C has dies for crimping and sizing pinfire cases as well.
4. After shooting, pull out the pin, remove the primer and clean the case.