You open the capsule and with both hands push towards the center. I pack mine tight and leave around a 10% space to close with. Typically a capsule will hold 1/4 teaspoon of powder.
When grinding the myrrh, be careful as it is the same as glass. If you leave myrrh in your coffee grinder and go the next day to remove, the myrrh will harden and trying to move it with your fingers can cause cuts. So grind, move it to a clean container to fill the capsules with.
I also put the powder and the oil in a face cream I had with some essential oils and it is very good for pain.
Dr. Mercola tells of making an oil but did not find it worked as good as the cream.