The first step is to cut off the pistol grip and finger guard from the gun. Once you have done this clean up the area and make sure you have a nice level place to work with.
Next measure where you want the hole to go. I did this by holding the weapon up to the arm with the magnet in it and eyeballing it. It wasn't too difficult.
Next drill your hole and insert the magnet. Note this magnet has the shiny side out instead of the colored. This means the magnets will stick together. I find that color coding one side of the magnet makes this process super easy.
Next time I will show you the completed product and give you a link to where you can download the entire tutorial on making swappable magnets.