How to paste your Meta Tag in your BigCommerce homepage
Copy the meta tag found in your Google Merchant Center, if it's not already automatically added during your setup.
Login to your BigCommerce Admin Panel.
Click Advanced Settings > Data Solutions (formerly Web Analytics)
Click the Site Verification Tags tab.
Paste the meta tag into the field provided. If you had added any other code in the past, make sure that you paste the meta tag on a separate line.
Finish up by clicking Save.
Return to Google Merchant Center. Click on VERIFY URL and then click on CLAIM URL. For more information, go back to the Claim Your Website article.