How can I use my Apple ID balance on Game Center?

Based on your screenshot, you need to add funds to your Apple ID balance, see -> Add money to your Apple ID balance

Add money to your Apple ID balance – Apple Support (UK)

App Store & iTunes gift card:

Apple Gift Card - Apple (UK)

What you can buy with your Apple Gift Card or Apple ID balance

What you can buy with your Apple Gift Card or Apple ID balance – Apple Support (UK)

How to redeem your Apple Gift Card or App Store & iTunes gift card

How to redeem your Apple Gift Card or App Store & iTunes gift card – Apple Support (UK)

If you update your payment method or add funds to your Apple ID balance, It would take about 1 to 3 business days in order to process.

See -> Check your Apple ID balance

Check your Apple ID balance – Apple Support (UK)

To do that, your going to have to have enough money for the in-app purchase you want. You can get money in your Apple ID by adding a payment method, or by getting a Apple Gift Card. To make the in-app purchase, you have to do it in the game. Tap the button (that shows ether the amount of money or says Buy, if shown) to buy it, and then tap Purchase. You may be prompted to use Touch ID, Face ID, or your Apple ID password. You also may be prompted to press the side button on your iPhone. It depends on what device you are using. Once you got that out of the way, your all done, and your purchase is made! Hope this helps!