To change the locking settings on your product(s), navigate to the "Settings" drop-down menu. Select "Products" to get to the Product Management page.
Navigate to the product that you want to edit the locking settings of. Hover over it and click the "Edit" button.
You will see a box pop up that will allow you to edit your product's locking settings.
Product Locking Settings: Lock for changes once paid
Checking this box will ensure that your registrants cannot change what they've selected after the product has been paid for. This is selected by default.
Product Locking Settings: Lock once added to cartChecking this box will ensure that once this product has been added to a cart, it cannot be removed. This is especially useful for registration fees.