It's pretty straightforward; get a copy of Partitionmagic, run it, hit "Create New Partition", create a new partition (I recommend it be at least 6GB) and make sure the partition type is Linux ext2 (or ext3 would be better, if available).
Then create another partition. This one should be two times the size of the amount of RAM you have. Make sure the partition type on this partition is Linux swap.
Hopefully that helps.