Frances, you have a wireless router don't you? (that's the first step, if you want to do it wirelessly!)
THEN: Apple (in the menu bar)->System Preferences->Internet & Network->Sharing
In the Sharing window, click on "Services" make sure that "Personal File Sharing" is checked. You may also want to check Printer Sharing (and I have FTP sharing checked as well - another way of logging into someone else's 'puter). Under the Firewall tab, make sure that "Personal File Sharing" is checked and the Firewall is ON. (says at very top - and the radio button will say "stop") Leave the Internet tab alone - that's for sharing one connection via one of the Macs, and that's not what you want to do if you have a wireless router.
Next, make sure that AppleTalk is turned on for both computers. Network Preferences->Show "Airport"->Apple Talk->Click on "Make AppleTalk active"
You need to do this for every Mac that you want to be able to share with on the wireless network.
Once you've done that, you should be able to see the other Macs on the network. Next you have to designate what is "shared" on each of the computers - otherwise all you'll see is the the Public folder. I generally just designate the entire home folder of each of my users as shared, since I'm the "system admin" around here.
You do that by clicking on the folder in the finder ->Get Info->Ownership and Permissions and then Others and make sure it's set to Read and Write. (and that all the other categories are set to Read and Write) You may have to click on the little lock icon to change things.
The other alternative is to put things you want to share in your Public folder, but that's more for non-family/higher security situations as far as I'm concerned. But then I'm MOM. The all-powerful.
