I have a working Ubuntu 14 LTS install in a VirtualBox jail. Where in the docs do I find how to add additional storage from outside the jail into the jail. Using FreeNAS 9.10.
Adding storage for a VirtualBox jail is the same as adding it for any other kind of jail: http://doc.freenas.org/9.10/freenas_jails.html#add-storage. If you want to make that storage available to a VM in that jail, though, that's another issue, and you'll need to install the Guest Additions in your VM and consult the VirtualBox docs about shared folders.