Basic steps:

  1. login to your local server (example.com) and get a session jwt
  2. node lemmyhelper_commandline.js communitiestickle --jwt blahbalblahtoken --server0 https://sh.itjust.works/ --server1 https:/example.com/

I suggest avoiding Lemmy.ml as a source server, it is extremely overloaded for weeks.

Regarding step 1, you can get the jwt from your web browser, the server logs of your instance (when you hit it from a web browser), or using lemmy-helper: node lemmyhelper_commandline.js testlogin --help

Code is a real mess, but some cool abilities are coming together.