This follows the same process as playing a card. See rule 349. Playing Cards for more information. 1. This behaves, once activated, like a spell without an associated card.
§ 145.2.a Core Rules PDF (officieel)
§ 145 Units may have Activated Abilities.
§ 145.2 The Activated Ability of Units may be executed at any time during the controlling player's Main Phase during an Open State, and not during a Showdown.
