This Apple Account has not yet been used with the iTunes/App Store -
On a Mac;
• Open the System Settings app (in the menu)
• Chose your Apple Account
• Choose Payment & Shipping
• Add a payment method to your account details
On an iOS/iPadOS device;
• Open the Settings app
• Chose your Apple Account
• Choose Payment & Shipping
• Add a payment method to your account details
Alternatively -
On a Mac;
• Open the System Settings app (in the menu)
• Choose your Apple Account
• Choose Media & Purchases
• Choose View Account
• Choose Manage Payments
• Add a payment method to your account details
On an iOS/iPadOS device;
• Open the Settings app
• Choose your Apple Account
• Choose Media & Purchases
• Choose View Account
• Choose Manage Payments
• Add a payment method to your account details
You can find the acceptable payment methods for your country here;
https://support.apple.com/es/HT202631
M1 Mac mini, macOS 15.2; Watch, series 10 GPS-only, watchOS 11.2; iPhone 16, iOS 18.2; TV 4th Gen, tvOS 18.2; HomePods, audioOS 18.2 and Airport Express w/ Airplay 2