Enable Datalayer?

I'm trying to enable the data layer on Squarespace... I've been working with a developer and this a message I received from the developer: We need to use Google Tag Manager to configure the FB Pixel and FB Conversion API on your website using Stape io server for service-side tagging configuration. However DataLayer is required for FB Pixel and Conversion API configuration using GTM. Otherwise we can't track e-commerce events and parameters like - product name, product prices, product IDs, etc.
 

I'm hoping I can do this myself, but have a feeling it's above my pay grade. Please help in any way!!!