To give you a bit of a hint in the right direction, you'll need to use the "mount" command if you want to manually mount and unmount (umount) the additional drive (won't auto mount on boot). If you want it to always mount, then you'll want to add an entry to yoru /etc/fstab file.

Sorry I can't just give you explicit answers but I don't recall all the details OTTOMH and would rather just point you in the right direction than risk misguiding you...

As to where you mount it, that will depend on what sort of data it will contain and your purposes for it's use.

Also FWIW if you just want to create additional space in the VM (not neccessarily a separate volume), then IIRC the OVA uses LVM so this blog post should still be relevant - it's a little dated but AFAIK should still work.