Do I need to write any code to use AppifyCommerce – Social Chat?

No. AppifyCommerce – Social Chat is built for non-developers. Once you activate the plugin it loads everything it needs (including its styles and scripts) automatically, so the WhatsApp button appears on your site without editing your theme or adding a shortcode. You configure the number, message and appearance from the Appify Chat settings page and click Save — that's all it takes.