There are several steps to allow your customers to add discussions about your products.

Step 1: Go to Settings->General->Advanced to enable '
Allow Product Discussion' and remember to save the change.

Step 2: Customers are now able to leave comments about the products on the product page beside the 'Description' tab.

Step 3: You'll need to approve the comments to make them public. You can also reply to the comments from your customers.

Once you've approved them, the comments will be displayed on your product pages!