Two ways: use the System 6 installer (which gives an option for AppleTalk), or drag the files from the System 6 install disks to the System Folder on your hard drive. I think that you only need the AppleTalk extension, but it has been so long since I've done it that I forget. If you choose the latter, and you don't already have the Chooser in your Apple Menu, you will have install it with the Font/DA utility.