I need to have a hostname or URL madeup so that internet users can access an application via its name, similar to website. I have a public IP for this purpose.
What should i tell my isp specifically to do so that this IP gets registered by hostname(like www.check.com)
You simply need to tell whoever is responsible for your public DNS servers to add the following entry -
If it is a mail server they will need to add additional MX records so it's best to tell them the purpose of the server.