In order to add custom code to the HTML in the Magento take the following steps.

1. Navigate to Admin Panel > Content > Configuration.

2. Choose the store view you want the head tag to be changed on or select Global in order to change it on every store view.

3. Find the HTML Head section and add your code in the Scripts and Style Sheets field.

Once the changes have been performed don’t forget to press the Save Configuration button and flush Magento Cache.

The code will be added to all pages on your site and Social Proofy will start working.

Now verify your pixel in Social Proofy.