On your Newton device:

Install the Newton Internet Enabler (NIE) to enable ethernet protocols.

Install a driver for your wireless PC card. See the WikiWikiNewt for further information.

Install a package that adds an ethernet connection option to the Newton Dock app. For example, EthernetDock.pkg replaces the Dock app’s AppleTalk option, or Dock_TCP-1.2-en.pkg adds a TCP/IP connection option.
On your Macintosh computer:

Launch System Preferences.
You need to allow TCP/IP access to Newton Connection through your firewall.

Click the Security icon and then the Firewall tab within the panel that appears. Allow incoming connections to the NCX application.

Close the System Preferences window.