If you're not pixeling, you're losing. For most CMS this is fairly straightforward. Wordpress - find a plugin. Shopify - find the Facebook Id field in Settings (while you're there, install a FB shop and set up a Dynamic Product Catalog). Etsy - Facebook Marketing (some creativity required, get them to add the pixel, then change your mind on running ads through Etsy *pixel stays placed*). All else, check the FB integrations list.