How do you craft rune essence

You can't craft rune essence--you mine it. First, you have to complete the Rune Mysteries quest, which is pretty easy. Then, you left click on either the head wizard in the wizard tower or the wizard who sells runes in Varrock (I forgot his name) and click "teleport". He will teleport you to a mining place for only rune essence. And that's how you mine rune ess!