Way to unlock: Automatically, during the Haven's Best and Brightest side quest.
The quest-giver: The Apothecary (M2,5)
This quest becomes available after you see the Apothecary in the South-Western part of Haven (M2,5). Talk to the Apothecary about brewing and upgrading potions and equipping your party members with them. At the same time, you will receive a quest. It consists in finding out about the functioning of the equipping table (Equip Potions). The table is in the cottage, where you met the Apothecary.