Pet is your companion in the fights with zombies. 

You can get pets in the Missions ( zombie mode) by using Pet vouchers. To equip the pet you want, you need to tap its icon first, then tap the Equip button. 

Please note that each pet has different stats, which can influence the outcome of the battle. To level up your pet, you can feed it by using the pet bones. 

How to fuse pets.

You can also fuse different pets with each other. To do that, you need to tap the pet icon, then tap the Fuse button and choose the pets you want to fuse with the one you have chosen.