fdisk is already installed. However, I don't recommend using PelicanHPC for partitioning hard disks. I would install a general purpose distro to the hard disk, and take care of partitioning while doing that. There are also live CDs that are oriented towards that sort of thing.
http://partedmagic.com/ comes to mind. I have never used it, so this is not an endorsement, just a reminder that specialized tools are available.