1. Purchase a pickaxe from the shop.
2. Head to the otherside of the home area, passed the bridge and you'll see the mining area.
Mine some rocks!
3. The portal in the mining area will take you to the rune essence area, that is where you will get them for runecrafting.
4. Right next to the mining area is the altar, just click the altar and it will give you experience and air runes at the cost of your essence.