Upsells
Add Upsells to the course by adding an Upsell on the Thank you page. Open the Thank you page in the Editor, Add the Upsell & select a course for the Upsell.
Order Bump
Add Order Bumps to the course by adding an Order Bump on the Checkout page. Open the Checkout page in the Editor, Add the Order Bump and select a course for the Order Bump