370. Activated Abilities are repeatable effects with a cost. They follow a process of going onto the chain and resolving, similar to Playing a Card. See rule 346. Playing Cards for more information.

370.1. Activated Abilities are recognized by the presence of a ":" in the text of the card, preceded by a cost and succeeded by an effect. Example: "[2]: Draw 1" is an activated ability. The cost is 2 energy. The effect is to draw 1 card.

370.2. Activated Abilities use the chain.

370.2.a. Declare activation of the Ability.
370.2.a.1. The ability goes on the chain but has no card to represent it, so players need to take note that it is now a Closed State.
370.2.b. Proceed with executing the Chain.
370.2.b.1. Follow the steps of “Playing or Activating Abilities” in rule 386 . This ability will become a Pending Chain Item.
370.2.b.2. Opponents have an opportunity to respond, as appropriate, as if a card was played onto the chain.
370.2.b.3. If no further action is taken, execute the Activated Ability.