I just recently installed the card reader. How do I input an amount for the charge?

You can input a charge amount using your card reader through the QuickBooks GoPayment app, Joann25.

To begin, let's ensure that your mobile device's Bluetooth is turned on and that your card reader is successfully connected.

If you're creating a new sales. Here's how:

1. Open your QuickBooks GoPayment app.
2. Click the Plus (+) icon and select New sale.
3. Enter the amount you want to charge or select Items to add products and services.
4. Select Review Order.  
5. Ensure your amounts are correct and click Charge. Then pick your card reader.

If you need to accept a payment for an existing invoice or a payment in advance, refer to this article: Process payments in the QuickBooks mobile and QuickBooks GoPayment apps.

You can revisit this thread if you have follow-up questions.