Your package will include an instruction sheet which states the following:
Instructions for Burning Charcoal Cups:
Hold the edge of the charcoal cup in a steady flame for a minute or two, a lit candle works well for this.
Be careful not to burn your fingers, tongs can be helpful.
Once there is a red edge you can rest it in a fireproof dish, and it will continue to burn.
Caution, charcoal cups burn very hot. Even in a stone bowl you will want to put a potholder or something underneath so you don’t damage your furniture.