Add 3rd party components or plug-ins to your website
Documentation | Webpages | Plug-ins
The webpage editor comes with a Javascript component, which you can use to load plugins. Using the CSS Class Wholesite, will also see this plugin appear on every webpage.
You cannot add plugins to system pages, only webpages.
Add a Javascript component to your home page or the webpage you want your HelloBar to appear and add this to the javascript section:
var scriptId = 'hellowBar'; // Replace with your desired ID
// Replace with your actual script URL
var scriptSrc='https://my.hellobar.com/getthisscriptnamefromyourhellobaraccount.js';
if (!document.getElementById(scriptId)) {
var script = document.createElement('script');
script.id = scriptId;
script.src = scriptSrc;
document.head.appendChild(script);
}