Around 64 MB is a good size to assign to swap space on a modern machine with 32-64 MB of memory. The maximum size a single swap partition can be is 128 MB, but you can have as many as you like. One machine I am currently setting up as a high performance Web server has four 128 MB swap partitions. If you really cannot spare another partition for swap, then you can run without it, and even have swap as a temporary file. Using fdisk To use fdisk you simply make new partitions.
Cylinders are a low level measure of disk capacity.
For efficiency reasons it is best to give your sizes in cylinders. This gives the underlying drivers a performance gain as the size of the partitions matches the physical characteristics of the disk. You can make a partition to approximately the right size by looking at how big a cylinder is in MB and multiplying it up. To make a new partition of 500 MB that works out at roughly 63 cylinders. The easiest way to get a partition about right is to make it then press p to see what the actual size is.