How do you use money on App Store/iTunes account for inapp purchases

Before you can add funds to your Apple ID, you must have a valid payment method on file. Learn about the payment methods that you can use with your Apple ID. See how to Add funds to your Apple ID https://support.apple.com/en-us/HT208687  Note that "after you authorize the payment, the funds ... [are credited] to your Apple ID. Then, you can use the credit to make purchases from the App Store or iTunes store.

Normally, all charges will be deducted from your account, but you need a valid card on file in case the total cost of the purchases is more than the account balance.

Apple ID payment information - change.        

If necessary, contact iTunes Support. Either use the form or scroll to the bottom of the page in the 2nd link. Follow through the screens to get a chat or telephone option.  

iTunes Store - Contact Us - Official Apple Support.       

iTunes Support – world wide        

What happens when you try to make a purchase? Error message(s)? You can add App Store/iTunes Gift cards to your account. You need enough money to cover the cost of the purchase, plus any applicable taxes.

App Store & iTunes Gift Cards by Email.     

Gift cards redeem.    

Gift Card - can’t redeem.    

If you see a message that says 'Your account has been disabled in the App Store and iTunes' - Apple Support.    

Contact iTunes Support.  

iTunes Support – world wide        

Buy iTunes gift card(s) and redeem it to your account.

Or use a valid credit card with your name on it, issued by your bank.

You are welcome.

I used my husband’s credit card when he received some more random payments on iTunes he blocked his card and then my account get blocked