Several varieties of partitioning programs have been adapted by Debian developers to work on various types of hard disks and computer architectures. Following is a list of the program(s) applicable for your architecture.
Recommended partitioning tool in Debian. This Swiss army knife can also resize partitions, create filesystems (“format” in Windows speak) and assign them to the mountpoints.
The original Linux disk partitioner, good for gurus.
Be careful if you have existing FreeBSD partitions on your machine. The installation kernels include support for these partitions, but the way that fdisk represents them (or not) can make the device names differ. See the Linux+FreeBSD HOWTO.
A simple-to-use, full-screen disk partitioner for the rest of us.
Note that cfdisk doesn't understand FreeBSD partitions at all, and, again, device names may differ as a result.
One of these programs will be run by default when you select(or similar). It may be possible to use a different partitioning tool from the command line on VT2, but this is not recommended.
Remember to mark your boot partition as “Bootable”.