Charms give you various benefits and are made by combining two crystals (one head crystal and one tail crystal) together. If you don't have enough crystals you'll need to complete 3 goals and level up to collect crystals.

Once you have enough crystals you can create charms just like this:

1. Open the crystal chest (bottom right corner) to open the crafting menu

(Optional) If the costume menu was open previously, then the costume menu will open.  Tap on the crafting button on the right. 

2. Drag 1 head crystal and 1 tail crystal of your choice onto the crafting board. Remember every combinination will create different charms.

3. Once you carefully arrange the crystals, we then get to work....

...and that's it! You've made your first charm.