You can use the Square and the Square Reader in tandem with Change to process credit cards.
After you've rung up an order and it's time to enter payment, switch to the Square app and charge the customer's card using Square's Custom Amount screen.
NOTE:
You can quickly switch between apps by using a four-finger swipe.
Once you've charged the card in Square, return to the Change Payment Screen and enter the amount charged under Other Credit Card. Tap Apply or Checkout to complete the order.
If you'd like to process credit cards using Change, learn more about accepting credit cards.