I'm using NginX, but the principles are the same in that "beginner" needs to set up virtual hosts for the web server. That Fedora link isn't sufficient information. I do agree that setting up virutal box is a weird approach, assuming "beginner" is trying to take one droplet and create two virtual servers. Apache and NginX can keep the websites isolated, though they will share the same IP address.
I'm using FreeBSD, so I can't be of much more help, (Well providing people think I helped at all. ;-)) Here is a google hit regading virutal hosts, but obviously untested by me.
Doing a quick scan of the article, I don't a mention of DNS, but obviously you have to set up DNS for each domain, even if the actual IP is the same.
The Apache web server is the most popular way to serve web content on the internet. Apache has the ability to serve multiple domains from a single server by using a mechanism called "virtual hosts". If a virtual host is configured correctly for each domain, the web server can correctly route traffic to the appropriate files based on the domain name requested. In this guide, we'll demonstrate how to configure Apache virtual hosts on an Ubuntu 14.04 VPS.