First you hold the button, until you are at the element you want to choose. Then you can add more power to your attack, when you select the element again or you can select the element at the left or right to change the position. Whan you click you release the element and attack the monster.
Example: A Fire-Monster spawn in the direction of metal. Then you can summon water or metal to attack, but earth would be stronger again fire, because wood is strong again water, water again metal, metal again earth, earth again fire and fire again wood. Be careful not to summon wood, because this is weak again fire and maybe heal the monster. Now you have summoned Earth, you must select metal to get the earth to the right place. Now you can click to release the element and attack the monster.
When you was to slow, the monster get closer to you or change the position.