Register your domain name to identify your business

Contact a registrar - a company that registers domain names.
The most common registrar is Godaddy, but many others like Hover.com, Hostinger, and Bluehost.

Carefully pick out what goes to the left of the domain name extensions.
The common domain name extensions are .com, .net, .info, and .org, so you need to choose what goes before all these.

Register your domain name by yourself instead of getting someone else to do it for you.
You become the legal owner only if your name is listed as the domain name's registrant.

Buy a bunch of domain names that represent your current business.
This will prevent others from purchasing similar domain names that could confuse the marketplace.

Remember to renew your domain name.
Make sure that your credit card and other information for the service are up-to-date for automatic renewal.