How do I access Virtualbox internal IP from host machine?

For old installations of Virtualbox

I finally found the solution, on the third page of Google. :/ There was a great power point at http://www.slideshare.net/powerhan96/networking-between-host-and-guest-v-ms-in-virtual-box which explained everything that needed to be done. In addition, on the Virtual Manager, I had to make it fullscreen, File->Preferences->Network->Host Only Networks->Add. I needed both a Host-Only adapter and an NAT adapter for it to work both ways, which the powerpoint explains.

Update: Virtualbox 5.2

In Virtualbox 5.2, stop your VM. From the main menu, select "Global Tools-> Host Network Manager". Click "Create", and a new Host-Only Network called vboxnet0 should be created. Navigate back to the main menu by clicking "Machine Tools". From here, right-click on your VM image and go to "Settings->Network", and attach to your new Host-only Adapter called vboxnet0. When you restart your VM, its IP should have changed from 10.0.*.* to 192.168.*.*, and should now be accessible from your host machine.