I'm in the process of setting up a 5 computer network (over ethernet) to share a DSL connection. I understand the DSL "modem"/router, switch, their functions and what they're for. I want to learn more about telling the computers to realize they're on a network and talk to each other. (Is this automatic?... I don't have those components connected yet.) Specifically I have 2 of the routers, which have wired AND wireless capabilities. I want the knowledge to experiment with using the second one as an external wireless card on one of the machines.

I REALIZE THIS IS THE WRONG FORUM TO LOOK FOR THOSE ANSWERS, I'M JUST LOOKING FOR A TUTORIAL. Thanks!

This is one of those areas where you say it is easy, once you know how. Each computer must be named or have an ip address. Then all are established in network places.
There are excellent good tutorials at www.microsoft.com, and most router manufacturers have them. The microsoft tutorial is in seven parts, you can search at Microsoft with "How to 'Set Up a Small Netowork".
On Google, search for Network Setup for a Small Office, and Setup a Small Network.
There are many, many such tutorials at smartcomputing.com, and similar.
Secrets: Name and setup your work group first. Use simple, simple, unique names for each component. Good, not cheap cables, or good, not cheap, wireless units. Patience, lots of it, and thinking about what you are doing. Take your time.
Once done, you will never have to think about it again, but it is confusing at first.
If you can find one of the Networking magazines on the racks of major stores, they are better than books. For more than 8 computers and printers, you may need the book.
Be able to see all your components in My Network Places. Printers must have network ethernet ports or be nameable with IP addresses.