How I use the money in my apple account when I try to buy an app
it won’t let me me use it for the apps
It should use it automatically unless there is an issue with your payment method and it stopped being verified.
If its requesting you verify your payment settings, then there is an issue with the payment method on file and will not be able to proceed with payment. Once verified, it will not charge the credit or debit card and use your Apple ID balance instead.