how do i verify my payment method?

Hello ~ Take a look here.. .*Eric Root* has put it best.

I can't verify my payment information...n… - Apple Community

~Katana-San~

To verify your payment information:

Sign in to your Apple ID account page and edit / update your Apple ID details.

https://appleid.apple.com

On the Sidebar click Payment methods -> then tap Payments Methods and tap Manage payment method.