Hello Robert,
the Domain Name represents the IP-Address, its just easier to memorize :-).
This means, when a user types a Domain Name into a brwoser, the browser has to ask someone who knows the according IP-Address for this Domain Name.
The request is sent to a Doman Name Server (DNS). Once resolved, the browser gets directed to the machine that holds your Webserver.
You have to take care that your domain name is listed in the DNS.
But who to achieve that? Look at your domain seller, whether they provide you with the ability to set the domain name matching your IP-Address. It maybe take up to 72 hours until your server is reachable under its domain name.
Do you run your webserver on a local machine in your office? Do you have a static or a dynamic IP-Address?
If you have a dynamic one, that changes every 24 hours, you will most likely need to use a service like
www.DynDNS.org or
www.No-Ip.com. There you can get a (sub-)domain name like Roberts-Webserver.dyndns.org or something like that. They offer a software, that updates their DNS with your dynamic IP-Address once a day, so that you are reachable even with changing IPs.
However, you can now make
www.roberts-webserver.com pointing to roberts-webserver.dyndns.org which points to your IP of today.
hth
Wolfgang