I can see my "website" locally but how do I get it to show up online? Does it need a domain name per se or can't I just get DNS somehow to pick up my IP address and put it online or something, I don't know. I've got a domain name registered, if that helps.
If I understand correctly, you have a virtual machine containing an Apache server hosting the default "It works!" page. In order for this to be accessible from the Internet, it must first be accessible from outside the host machine (the host machine is the one running the Virtualbox software).
To do this, open the virtual machine's Settings dialogue, and from the Network tab choose "Bridged adapter".
This will give the virtual server an I.P. address on your network which you can discover by running ifconfig from the server - look for the address following inet addr:, it will probably be something similar to e.g. 192.168.1.10. Then, type that I.P. address into the host machine's web browser and you should again see the "It work!" page.
At this point, all that's necessary to access it from the Internet is to change settings on your home Internet connection's router so that, rather than blocking incoming web traffic, it directs it to your new server. This is called 'port forwarding' and is standard fayre on most routers, just log in to your router's web interface and you will find it. (You may need to keep that I.P. address handy.)
It appears from your question your knowledge is really quite basic, and rather than playing with putting it on the Internet, I would advise you to keep things local (just on your home network). One slight misconfiguration on an Internet-facing server can be catastrophic.
