Now that you have an Attuned Rock Crystal you can make use of the Ritual Pedestal. This will require a structure built below it. Check your Tome for full instructions. Once built, you can throw in your newly acquired Attuned Rock Crystal. Be sure to illuminate the multiblock structure so that snow will not accumulate on the blocks and cancel the ritual.
This Pedestal acts like a beacon. Each area of effect will be different depending on the attunement of the crystal. This beacon can have up to a 20 block radius and is dependant on the Size and Purity stats of the crystal you use (the Cutting attribute does not matter). You can remove the Attuned Crystal from the Pedestal by sneak-right-clicking it.