1. First, you must be on the 3.1 PTR client ;)
2. In Interface Options, under Controls, select to use the Equipment Manager
3. Open your character window and click the new Gear Manager icon in the upper right
4. Create a gear set
5. Click the EventEquip icon between the Delete and Save buttons in the Equipment Manager window
6. Pick an event, then a set to go with it. Click Save.