Final answer:
To enable QuickBooks to automatically apply discounts and credits, navigate to Edit > Preferences > Bills > Company Preferences and check the appropriate options to automatically apply discounts and credits.
Step-by-step explanation:
To set up QuickBooks to automatically use discounts and credits, go to the 'Edit' menu and select 'Preferences'. Then select 'Bills' from the menu on the left. Once in the 'Bills' section, navigate to the 'Company Preferences' tab. Here, you will find options to automatically apply discounts and credits. For discounts, you can specify the default discount account where QuickBooks will record the discount transactions. For credits, you select the checkbox to 'Automatically use credits'. This ensures QuickBooks will automatically apply available credits to the next bill you enter for the same vendor.