Open the Google Play Store app
Tap your profile icon
Tap Payments & subscriptions
Tap Payment methods
Add a payment method
Choose a card, bank account, PayPal, or other available option
Enter your payment details
Save the payment method
To add Google Play balance, buy a Google Play gift card
Redeem the gift card in the Play Store
Tap your profile icon
Tap Payments & subscriptions
Tap Redeem code
Enter the code and tap Redeem
Confirm the balance in your Google Play account