Please checkout this (ad-free) update post I've done on a spare blog. Feel free to bookmark it and check everynow and again for update if ads are pissing you off. Always feel free to ad-block them for now though if you want. I'll let you know when you can disable the ad blocker again, only if you want to see the ads. They should look nice and neat in the end.
I'll assume there is one computer already working, and you want to add another. So :
1) Does the first computer plug into a router via a LAN cable ?
2) Does the router have more than one LAN port on the back ?
If both are yes, then just plug the second computer into any of the spare LAN ports on the router and it should just work.
If 2 is no, then you'd need a switch to expand the single LAN port to "multiple". Connect the single LAN port on router to the switch, then each of the computers to other ports on the switch - then it should all just work.
If the answer to 1 is no, then more information needed.