What version of System 6 are you using? There are several different versions with extremely varied support and capabilities, particularly with regards to networking. Also, what machine are you trying to do this on? If it's a [relatively] more recent machine (Plus, SE, Mac II, etc.), it's going to be a lot easier than if it's a 512K. Finally, what vintage of machine are you trying to connect to via AppleTalk?
It's been a long time since I've done this to my 512Ke, but the first thing I would try is downloading Apple's Network Software Installer, which contains the latest versions of System 6-compatible AppleTalk and EtherTalk software. For this, you need to be running at least 6.0.5.
The 1.44 MB floppy version is here.
The 800K floppy version is here.
If this doesn't work for you, or you're running an older version of System 6, post back and we'll keep working on it.