1. Register your domain name to one of the .com, .org. .net or whatever TLD registry. Don't rely on "free" DNS providers such as freenom.
2. Once you have an account with a registry, create an A record that points to your IP.
3. If you have a residential IP and your ISP allows inbound ports then you can host your web, mail or whatever server you have on your local machine. With this setup, be extra prepared to deal with internet nasties.