From your Subscribers Dashboard, click on the " Site Popup Messages".

You'll then be prompted to sign up and create your account.

Once you do, Hello Bar installation will be the next step, and installing Hello Bar is just a simple process of copying the script code that you can find under your Account dashboard's "Summary Tab" as well as under " Installation Instructions" which can be found on the drop-down right below your account name...
...and then paste it to your website's admin page custom code/HTML viewer which usually either show letters HTML or this icon (<>).

Or if you have access to the main HTML document, you can insert the Hello Bar code preferably within the <body> section of the document.

Please see our following list of guides on how to install Hello Bar on different platforms

By the way, there is another alternative installation method for Hello Bar which is through Google Tag Manager. If you're not yet using it on your site, please try using Google Tag Manager so you'll have an alternative way to install Hello Bar. Here is the link to Hello Bar installation guide to Google Tag Manager:

Please see more about Hello Bar and the difference between Hello Bar popups and Subscribers push notification HERE