In your Shopify account, click Products in the left navigation panel. Select the product.
On the product page, copy the product number at the end of the URL. For example, this URL (https://YOURSTORENAME.myshopify.com/admin/products/559435389) has a product number of 559435389.
In Northpass, select the course. Click Settings.
Scroll to the Shopify section and paste the product ID in the field.
Click Update Course.