2. Click onto your publication
3. On the left, click onto "In-app Products"
4. At the top of the screen, click "Add new product"
NOTE: The product type and product ID cannot be changed once created and the ID cannot be used again.
5. Select "Managed product" for product type
6. Enter in a Product ID (Ex: com.publication.issue1)
a. Per Google, an ID should be composed of lower-case letters(a-z), numbers(0-9), underline(_) and dot(.)
b. It should also start with lower-case letters or numbers
7. Click Continue
8. Enter in a product Title (Ex: My Publication - Issue 1)
9. Enter in a product Description (Ex: Purchase Issue 1 of My Publication)
10. Enter in product Price, excluding tax
11. Click Save
Click here for the Google reference article