How can I mount a LVM volume with fdisk?
 

I have made an LVM group (named "system") that I need to mount to a directory.

The name of the LVM directory is "slash".

All I see with fdisk -l is the primary partitions (/dev/hda3 is where the LVM is already created)

You don't mount anything with FDisk - you use FSTAB to permanently mount file systems.