That's easy. To make .html files accessible to the rest of the internet, you upload them on a server. Now, there are 2 ways that you can achieve this.
1. Get hosting (free, paid)
2. Host it yourself
You can download WAMP server if you have Windows, or MAMP if you're running Mac. For Linux, it would be LAMP.
Once you've got your server running, put the .html files that you want accessible in the Document Root.