1. Log in to your Merchant Center and navigate to the "Settings" tab
2. Scroll down to "Presence/Review Sites"
3. Click the "Edit" button in the top right-hand corner of the Yelp box
4. Paste the URL of your Yelp page into the field at the bottom of the Yelp box
5. Click "Save Changes" in the top right-hand corner of the Yelp box
A direct link to leave a review on the page will generate upon saving.