The method to add a payment method to the Google Store is as follows:

1. Open the Google account.

2. Click the profile icon in the upper right corner of the screen.

3. In the menu that opens, select Payment.

4. Click to add a payment method.

5. In the pop-up window, select the payment method you want to add, such as credit card, debit card, PayPal, etc.

6. Select the payment method and enter relevant information, such as card number, expiration date, security code, etc.

7. Click the Save button.