Our go-to stones for channeling are danburite, celestite and apophyllite. And quite honestly, any high-vibrational, crown chakra stone works well. Selenite and amethyst (both in your kit) would be great options as well.
When channeling place the stone(s) in your palms and sit upright. Breathe into the heart center until you feel yourself "drop in" to meditation. Once you are centered and clear, place your attention about an inch or two above the top of your head. Patiently keep your attention in this area and notice any sensation. Channeled messages usually come for us immediately after a tingling and burning sensation begins in this area.
A pendulum is a great tool to use prior to channeling. When I (Kayla) used to do channeled readings, I would say out loud, "I invite all spirits, guides, angels and departed loved ones to channel messages through me on behalf of ________ (the person I was reading for) for their highest good. I invite you to come through me now in meditation and send clear, articulate, helpful messages ." I would then ask the pendulum if the spirits were present. If it said no, I took a deep breath, closed my eyes, meditated for a moment and then asked again. Without fail, they always showed up.