This page details how to submit and confirm your Google Customer Reviews participation once you've entered the sign-up flow in your Merchant Center account.
Agree to Google Customer Reviews programme agreement
Read the Google Customer Reviews agreement on behalf of your company, tick the agreement box and click Save & Continue.
After successfully signing up for Google Customer Reviews, 'Customer Reviews setup' will appear in the Tools section of your account. To get to the Tools section, click the tools icon 