How can I pay using my ZotoCash?: 

Anytime you initiate a transaction on Zoto, the system should automatically take some amount from your available ZotoCash balance. This may apply if your ZotoCash balance is not #0:00 at the point of your transaction.

However if the app does not automatically check the Use Zotocash box, check it and proceed to pay.

To accumulate your ZotoCash, remember to uncheck the ZotoCash option before proceeding on your recharge.