There are several ways to accomplish this but the easiest solution all round is to create a new specific “catch all” domain.
This new domain will be the site that appears when your server is accessed by it’s IP address.
The site that gets displayed currently is based on the first site on your system alphabetically, so we need to create a new one that supersedes all of our other domains. Simply create a new domain called 001Default.
Upload any default content to this newly created domain, alternatively you can link / forward this domain to any other URL if you want to use an already existing site on your server. Now whenever somebody visits your server by IP address they will either get the new content you have created or will be forwarded to the site of your choosing.