You will need to register a domain ie: kissinggame76.com
Unless you intend to host your infrastructure yourself , you will need a hosting company, many different types of hosting plans are available, but for the very simplest Splunk installation, you'll want a single dedicated server(virtual or physical)
There are loads of companys that provide these services , godaddy.com are one such that will do the above for you.
Dedicated Server Hosting
Your domain name will resolve to your hosted server.
You can then install Splunk on your hosted server.