On this screen is a list of partitions currently on disk and this menu (a simple Linux install used as an example):
Here is a list of the current disk partitions:
* hda (4096 MB)
\_hda1 100 MB Linux
\_hda2 256 MB Linux swap
\_hda3 3644 MB Linux
Do you wish to modify the above list using 'fdisk'?
1. yes
2. no / continue
>
If you select "1" or "y" you will ask to specify which disk you wish to partition. You can designate a disk by its /dev/ directory filename (hda, sda, or what have you). Once you have entered a disk the installer sends you into 'fdisk' as if you had typed:
fdisk /dev/[what-you-entered]
at a shell prompt. If you need help with fdisk please look at the man page for fdisk or places on the web like:
http://www.doc.ic.ac.uk/lab/labman/lookup-man.cgi?fdisk(8)
After you have modified the disk partitions to your satisfaction write them to disk and select "2" or "n" when asked to repartition to go on to the "Mount Points" screen.