There are two different routes you can use to perform this task. The first involves using the network and is good for large files or files that you need to access repeatedly from either platform. The second is via floppy disk which is good in that it doesn't rely ON the network, doesn't need you to have a username, but bad in that it can only handle small (< 1.4MB) files.
Login on the PC
Copy the files to h:\mac
Login on the Mac
You should see your files in the "Network" volume on the DeskTop.