What distribution are you using? I ask that because the commands may different for different ones. Also, have you heard of the mtools suite? They really are convient to use.
Anyway, here's something that may help.
Insert the floppy that you want to use.
To format it type:
Then, mount the floppy like this:
mount -t vfat /dev/fd0 /mnt/floppy
Make sure you mount point exists (that's the /mnt/floppy part of my example) first, but that's all there is to it.