How do people subscribe to them?

Subscribing to an RSS feed really is nothing more than telling your RSS client about the URL to that RSS XML file. The RSS client then regularily checks the URL for changes.

If your site is hand-made as you say, you would have to manually create and update the RSS file also. This is quite nuisance, not only because it is XML, but also because every feed entry needs its own unique UUID, which you need to create. Perhaps you could create a script that does it for you. Static site generators are usually able to automatically create an RSS feed for you.