Before you start you should set up Google wallet merchant account -https://support.google.com/wallet/business/answer/1619772
1. Log into google developer app play.google.com/apps/publish
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9. Verify if all values are correct, especially USD.
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10. Go to the top of page, press "Save" and change status to "Active".
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11. Repeat all the steps from point 4 in order to add next products.