You can monetize an app by charging customers to download it, by using In-App Purchasing (IAP), or by using Mobile Ads.
Please see this guide to updating your app's Pricing.
Please see this guide to IAP.
Please see this guide to Mobile Ads.
I don't see any live apps associated with your developer account. If you have trouble monetizing an app, please use the Contact Us form to contact our support team. You can let them know exactly how you are trying to monetize, what the issue is, and the name of the app.
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