To add a discount on a specific item, we will need to create a category called "Sale Items" and put any items we wish to discount into it. Here's how:

Creating New Category

Go to Products > Products > Website Products and click Add Category.

Name the category Sale Items. Set "Is Active" to "Yes."

Click Save Category in the upper right.

Adding Products to "Sales Items" Category

Now that we've created our category, we need to add the items that we want to discount.

Now go to Products > Add Product and enter all the product information for the item that you would like to create, and make sure to check the Sale Items so that it gets added to the correct category.

Creating the Discount

Now that we've set our product to be discounted in the appropriate category, let's now apply the discount!

Go to Product > Promotions > Catalog Price Rules

Click Add New Rule in the top right and enter the appropriate information into the Rule Information section.

 

Now click Conditions on the left sidebar.

Click the green "+" button underneath "If ALL  of these conditions are TRUE :"

In the dropdown menu that appears, click Category.

 

Now click on the "..." that appears after "Category contains" (next to the red "X")

 

 Click on the notepad-like icon.

 

Select the "Sale Items" category (or whichever category you would like to apply the discount to) then select the green checkmark at the top to apply this selection.

 

Now that we've selected which category to apply the discount to, we need to tell it what kind of discount it will be.

So on the left hand side we click on "ACTIONS".

Now we set the discount. You can set it by a certain percentage or by a fixed amount. For this tutorial I decided to do a $10 discount on the products in the "Sale Items" category. It looks like this:


Important Note: 

      After filling up all the fields necessary and choosing settings, make sure to click "Save and Apply" button at the top instead of just "Save rule" or "save and continue" so the Discount will apply to your website.