Our Ubuntu will be able to reach the Internet and see other Virtualbox machines as well. Now we want to setup the networks so that we can SSH from our Mac OS X into the Ubuntu. It is now mounted as a CD on our Ubuntu guest. Click on it and select the VBoxGuestAdditions.iso on desktop and click on "Open" and then on "OK". On the right side of the window is a small CD icon. Browse to "Storage" and click on the empty disc under Controller:IDE.Now close all Finder windows and head back to the running Virtualbox application.
We may want to install the Virtualbox Guest Additions to enable features like shared folders, etc.