Visit udemy.com and click the "Add to Cart" button while your mouse is over the course thumbnails you want to purchase. When you've finished browsing for classes and are ready to purchase them, click the shopping cart button in the upper right corner of the page. On the shopping cart page, find the box that reads "Enter Coupon" under "Promotions" on the right side of the page below your subtotal. Once you've pasted your coupon code into the box, click "Apply." When your code is validated, it will be immediately added to your order.