A cluster, for anyone wondering, in general terms, is a group of connected computers that work together to complete a task.
Step 1: Materials
4 Apple computers. I used G5 Intel imacs but you can use any Apple computer.
4 Category 5 Ethernet cables
1 10/100Mbps Ethernet switch (minimum 4 ports)
1 key board and mouse
In my case, I got all of the imac because they had broken/missing screens. All you need then is a monitor, VGA cable, and VGA adapter depending on the type of port on your Apple.