node on wireless network

It is already a node on the network if it connects and can browse the web. Does this happen?

The computer function on the internet, I am trying to share files,
printers, etc between the two laptops (windows7) and the desktop
(ubuntu). I would be nice top control the programs on the desktop from
the laptops

then that isn't a "node on the network". A network node is something in the LAN that isn't a switch/router or bridge (like a server, an enduser pc or a printer etc).

If you install samba in ubuntu you can share files from nautilus using right click. If you use Windows L:ive messenger on the Win7 systems it can cause issue. I suggest you read this:
http://thelinuxexperiment.com/linux/accessing-windows-7-shares-from-ubuntu-is-a-pain/

This is a minor point, but to dispel a common misconception: A router certainly is a node. It has a MAC address associated with it, so it's a layer-2 node. And it has IP addresses associated with it, so it's a layer-3 node as well.

Instead of arguing over my terminology, how about answering my question:
have a desktop using Ubuntu and connects to the internet using a wireless connection. How do I set it up on the wireless network so it can communicate with laptops that are connected and use windows 7

Once the Ubuntu system gets an IP from the router it is connected. "connected" doesn't mean "file sharing:

If you run:

smbtree

What is output?

WORKGROUP
 \\DESKTOP desktop server (Samba, Ubuntu)
  \\DESKTOP\IPC$ IPC Service (desktop server (Samba, Ubuntu))
  \\DESKTOP\print$ Printer Drivers

Ok is 'desktop' the name of the system you ran that from?

I went to Applications, accessories. terminal then typied in smbtree

Ok. If you have a firewall (you will at least have Windows Firewall) have you configured it to allow filesharing connections

I have charter communications security. I dont know how to set up this firewall thing

Sounds like the firewall may be blocking the link