Installation and configuring plug-in Google Customer Reviews First of all, a merchant has to sign up for Google merchant center account. The merchant's e-commerce store must comply with all the technical guidelines given by Google to successfully display a badge on the store. Check all technical guideline here. Read this answeres about code too. These answeres will help you to understand settings of plugin (ex. OPT_IN_STYLE) https://support.google.com/merchants/answer/7106244 You will be able to install and configure plugin very easy. If GCR badge is not showing
https://support.google.com/merchants/answer/7105655
https://support.google.com/merchants/answer/7105655#troubleshooting