Activating Items
Source Player Core pg. 282
While some items function automatically and grant constant benefits, others produce effects only when properly used. An activation lists the number of actions it takes and any traits of the activation and its effect. This information appears in the item's Activate entry.
Activating Invested Items
Source Player Core pg. 282
You can Activate an Item with the invested trait only if it's invested by you.
Manipulate Activations
Source Player Core pg. 282
If the activation entry for an item has the manipulate trait, you can activate it only if you're holding the item or touching it with a free hand.
Limited Activations
Source Player Core pg. 282
Some items can be activated only a certain number of times per day, resetting during your daily preparations. You retain the constant benefits of these items even when the activation requirements of these items can no longer be met.
Cast a Spell
Source Player Core pg. 282
If the activation entry for an item lists “Cast a Spell” after “Activate”, you must use the same action as casting the spell to Activate the Item, unless noted otherwise. You must have a spellcasting class feature to Activate an Item with this activation. All the normal traits of the spell apply when you cast it by Activating an Item.