Every website on the internet requires a domain name. A domain name is nothing more than an easy way for humans to remember how to reach your site. You could technically reach your website with an IP address, but telling someone to visit you at http://126.96.36.199 is probably not what you are after!
There are many top level domains (TLDs) available today but try and purchase your business name as a .com if at all possible. If your business name is already taken, the “whois” function (available where you are purchasing the domain from) will provide you with a contact name of the owner to check and and see if it’s available for purchase.
Step one is always purchasing a domain for your site.
Step two is hosting your domain.
Step three is making it awesome.