How can I set up subscriptions to different pages of my site?

I’m a beginner to web push and struggling to find in the documentation clear instructions on how to do things (is there a full user manual I am overlooking?) I have installed webpushr successfully on my Wordpress site and have received pushes, but I need help on the following.

I want users to be able to choose to be notified when (a) particular page(s) is/are updated on my site. They may want to be notified about just one page, or several, so each page should have its own opt-in.

How do I implement this? Are there step-by-step instructions anywhere? The segmentation section says ’ Example: send a push notification to only US based visitors who have previously visited a specific page on your site during the last 1 month’, but I can’t see an option when setting up segmentation rules to select a specific page.

A second issue I have, probably a stupid question, is when setting up a manual push, what is the URL you specify in the setup? Is it a page where the notification will appear, or is it to redirect the user to that URL if they click on the notification? I seem to only be able to get notifications to appear when I am on the page that is being updated. What I want is for the user to be notified whenever they are using the net that my page has been updated.

Thanks a lot