Once you have completed the settings tab for the product you can then assign courses and lectures to the product by selecting the "Courses" tab.

You can assign entire courses by selecting the course at the root level. All sub course and lectures will then be selected. Alternatively you can select individual lectures to assign them to the product. In this case all parent courses to the lecture will also be assigned to the product, however only the selected lectures will be accessible.

If additional lectures are created and added to courses, these will not be automatically added to the product even if the course the lecture is added to also added to the product. You must add the additional lectures manually.

If a product has additional courses or lectures added to it after users have subscribed to the product, the already subscribed users will also get access to the additional courses and lectures. This enables you to keep the products fresh and keep the students engaged. 

Also is true if you remove lectures and courses from the product. These will be removed from access for the users subscribed to this product.