Connecting a Beam.pro bot to someone's channel which is not my own

I've been following this guide on making a beam bot with Node.js. I have been able to log on to the bot with script, however, I can't work out how to connect to a stream which is not my own!

This is what I believe is the reinvent code:

function  createChatSocket (userId, channelId, endpoints, authkey) {
const socket = new BeamSocket(endpoints).boot();

// You don't need to wait for the socket to connect before calling methods,
// we spool them and run them when connected automatically!
socket.auth(channelId, userId, authkey)

I have tried manually setting 'channelId' but I just get errors :(

via David Parkinson