To submit your app as a paid app to the different app stores, you need to follow the general submission process with one additional step.
You first need to open developer accounts with the Apple App Store and Google Play. Make sure that you have paid the registration fees to the app stores ($99 annual fee to the Apple App Store and $25 one-time fee to Google Play). In addition, you need to create a Merchant Account with Google Play and create a Paid Applications contract with the Apple App Store.
For an overview of the entire submission process, click here.