File sharing on Mac OS 9 is somewhat poorly documented, so I'll show you the WAY:

Step 1: Unless you have a crossover cable, you need an ethernet switch to start file sharing.

Step 2: Start up the computers.

Step 3: Make sure AppleTalk is on on those machines, from either the option bar or the control panels under "AppleTalk"

Step 4: Open up the File Sharing control panel on one computer.

Step 5: Drag and drop your file you want to share into the file box. Make sure it is in a folder unless Program Linking is on.

Step 6: Make sure the file has read and write priveleges for the other computer.

Step 7: Open the chooser on the other computer, and choose the computer name.

Step 8: Open up the shared drive, and find the file.

Boom! You did it!