There is a bootstrapping problem with Newtons and new machines, and you may well just have to buy some old tools to do the business, things like an interconnect dongle. However, on unna.org, it's said that packages can be beamed to a Newton using the freeware IRDA Package Installer (according to the developer, at any rate) but then you need a late model black PowerBook like a Wallstreet to do the business.

I haven't tried it using that utility, mind. Perseverance, and a utility like Packtype or Packager, will likely come in handy.

This place is not a very active site on the Newton front. But there are good how to guides out there, including 'how to dos' with recent hardware. Have you searched?