During this event, you can use the Event Summon Ticket/11-Event Summon Ticket to have an increased chance of getting a Year III character and/or the associated character's Memory Fragment in the event Summon with Summon. This is usually done twice for a Year III character before they are added to the Basic Summon Pool and Memory Fragment Boxes. 

After they do their two rounds of being in the Drop Rate, they can eventually be found in the Lucky Wheel event.