Pick Up is a basic, activated ability with the following text: Once on your turn, this unit may pick up any number of artifacts here. Each unit can use its Pick Up ability once per turn. You may only pick up artifacts that aren't already being carried. Since Pick Up is an activated ability, you can only use it during the main phase on your turn while nothing is on the storyline. For example, you can't use the Pick Up ability while in the middle of the Move and Attack ability. If the unit has the ability to carry units (e.g. War Horse), then its Pick Up basic ability is modified from 'artifacts' to 'artifacts and/or target units.' See the 'Drop' and 'Carrying Units' codex entries for more details. An oversized unit may simultaneously Pick Up from all locations it occupies.