For the push notifications to work on your website, a service worker file needs to be uploaded on your root directory. The file is named firebase-messaging-sw.js and it should be uploaded such that it's available as https://your-site.com/service-worker.js
If you are already using a service worker on your site with some other name than firebase-messaging-sw.js now you can configure that in the subscribers dashboard. Subscribers will automatically register the configured service worker rather than the default one.
And for any reason, if you do not have access to the root directory of your site, you can upload the service worker to any subdirectory on your site and configure the path in the subscribers dashboard, please see our guide on how to install the Service Worker file HERE.
Subscribers will use the above two fields to find the correct service worker on your site and use that for push notifications.
For example - if you already have a service worker file named service-worker.js then you can configure the name in the site settings. We would consider the service worker on https://your-site.com/service-worker.js and if the folder where this file is available is under assets/js folder on your site, we would consider the service worker on https://your-site.com/assets/js/service-worker.js
Now if in any case your site backend or CMS site builder does not have any option to install the Service worker file, you can still use Subscribers, but the catch is you will enable, not the "Browser native prompt" but the "Modal" prompt only, please see more on Subscribers opt-in prompts HERE
Reach our to our team at support@subscribers.com if you have any questions or feedback.