Shirley,
If you mean you would like them to access the internet on your machine, from another user's machine, then you need to enable ICS, or Internet Connection Sharing on the Internet device. (Ethernet card for example, housing a cable modem)
I am assuming you are part of a network. Make sure that the two desktops can speak to each other, and share files etc....then goto the Network Connections area, and right click on the Internet connection you wish to share. Click on the far right tab (cant remember the names....im on a 98 PC atm) and click on Enable Internet Sharing.
Et viola!
Hope this helps you
Have a nice day
CBradshaw