To craft Runes and Charms, navigate to the crafting page from the home screen. There are four tiers of crafting - Beginner, Basic, Intermediate, and Master. By crafting you will earn crafting XP and unlock higher tiers. The higher tiers require more crafting materials but will give a higher percentage chance of crafting higher rarity items.
The rarity chart will show your chance to craft Runes or Charms and its rarity. The bar in the top left shows the crafting level. At higher levels you will unlock higher tier crafting recipes. This crafting experience will reset every Season and all Moonshards will be removed.