To begin, you first need to enable courses to be sold. To do this, click on Home then Customization, followed by Sell Settings. Check the box labelled Enable Course Settings.
From here, you can choose to set up Stripe or PayPal. Enter your information to set up your payment collection method, as well as the tax rate that you want to charge and the currency in which you want to be paid. Click Update at the bottom when you're done.
To enable a specific course to be sold, you will need to click on Teaching, then Courses, then click on the course that you want to sell.
Click on the Sell Settings tab and enable Available For Sale. You will then need to enter the sale price and membership length (how long a learner can access a course after payment is processed). Now all that you have to do is either embed the code in your website or use the direct link.