To assign discounts to products, click on Settings and press Products. You can also use the global search box and begin to type in "Products" to select the Product page.
Search for the product you would like to assign the discount to by typing the name in the "Product Name" box and click Search. A list of results will appear below.
To the left of the product ID, place a check in the box. Click the "Manage Selected products" box at the top of the page to open. In the box titled "Discount" start typing in the discount code name you created, (it will autofill), and hit Apply. This will assign the discount to all the products that are currently check marked. When a product is assigned a discount, it just means that the discount may be used on that product. Other restrictions may apply, depending on your discount variables. It is a good idea to double check the settings of your discount code to make sure it is up to date.
NOTE: You can find all products assigned to a specific discount by typing the discount code name and pressing the search button.