This is a step-by-step tutorial on how to install the Guest Additions on a VirtualBox Virtual Machine installed with Ubuntu 12.04 so that you can access a shared directory on the host computer. I initially tried to install the Guest Additions by selecting the “Install Guest Additions…” menu option under the Devices menu. Unfortunately, this didn’t work, and I’m not entirely sure why. So here are the steps that I took to get the Guest Additions successfully installed on my virtual machine.