Library Run is a special type of mission in the game that allows you to battle Zombies to collect Library Tickets. To access this mode, open the Missions menu from the main game screen and select Library Run.

In the newly opened window, you can see the available Zombie to attack, its strength, and the rewards for defeating it.

To attack the Zombie Boss, tap the Challenge button at the bottom of the screen. You will need 1 Library Key to initiate the attack.

After engaging in several battles against zombies, you can either continue defeating stronger enemies to improve your rewards or claim the rewards for the Zombies you have already defeated.