Ubuntu Networking :: Adding A Router To Dorm Room?

I am currently attending college and living in the dorms we have 3 either-net ports and 3 people in one room. So we bought a router so we could have more then three things plugged in. I figured out via wikis how to set it up to run as a switch but I would like to run it as my own subnet. I have search far and wide for a guide or explanation on how to do this but the only one that seemed to be what I wanted was a bit beyond me.

Code:

Picture of how we get internet
internet comes in through wall from schools router(s)
| ___
====|=======|___|==several pcs plugged into router

[code]....