First of all, you will need a developer account for either Android and iOS. For Android you pay a one time fee of 25 dollar, for iOS you need to pay 100 dollar per year. Since I just wanted to try things out, I chose the cheaper option. So I can tell you only about how it works for Android, but assume similar steps need to be taken for iOS.

To publish your app, you need to upload an .apk file (Android Package) in the Play Console together with some extra information such as some general information, screenshots and a description. In order to get this APK to the Play Store, you need to perform several steps:

1. In the sprinter environment you go to ‘Mobile App’ to publish for mobile app store. Here you can set permissions your app will need to perform certain actions. With some of these permissions enabled, Google may ask you to add a privacy policy. So only select the ones you really need.
2. To create your build package you click Publish for Mobile App Stores and follow the instructions until you get redirected to PhoneGap. Now your APK will be build and you can download it here.
3. Before you can publish this APK to the Android Play Store, you need to sign your APK. Android requires that all APKs be digitally signed with a certificate before they are installed on a device or updated. How to do this, you can find here: https://developer.android.com/studio/publish/app-signing
4. Upload the APK in the Play Console and wait a couple days until your App is approved.

Good luck!

See also the documentation here: https://docs.mendix.com/howto/mobile/publishing-a-mendix-hybrid-mobile-app-in-mobile-app-stores

Regards,

Ronald