To summon puzzles of various Greatmen in the Academy building, you must have Greatman Summon Tickets.

3 Normal Summon and 1 Premium Summon chances are given for free each day.

Also, you can obtain up to 2 Greatman Summon Tickets by completing the Daily Missions.

Once you have the Tickets, you can go to the University building, press Summon Greatman Puzzle from the pop-up menu and try your luck in summoning.