1. Go to the 'catalog' menu and select 'products price manager'.
2. Select a category from the drop down list that contains at least one product.
3. Click the 'edit' button, located under the red text.
4. Click 'add blank discounts'.
5. Choose the discount type (perecentage, actual price, or amount off).
6. Enter the 'minium quantity' and the 'discount value' for each of your quantity discounts.
7. Click update.