To get Node-RED running and working with MongoHQ, at this time (with Node-RED 0.5 being current) you'll need to use the latest development build of the software. This will add the authentication functions to the MongoDB node and allow Node-RED flows to connect to MongoHQ. The first part of this process is to get the Node-RED code which is hosted on GitHub. You will therefore need git to retrieve it.
You will also need Node.js installed to run it. On the Mac, if you don’t have Node but previously installed Homebrew, just run
brew install node. For other platforms, or for Homebrew-less Mac users, go to the Node.js site and click “Install” for an appropriate package.
You then should run
git clone https://github.com/node-red/node-red.git
At the command-line which will download all the source of Node-RED. Go into the directory...
npm install --production
which will then download most of the other packages required by Node-RED. When thats done, its more than likely you'll need to install the mongodb driver too, so run
npm install mongodb
You are now ready to run Node-RED. Type
and hit return to see the server start up. There'll be a lot of warnings about nodes not being set up; this is because they are nodes which require other drivers which we aren't using.
Finally, point your web browser at your localhost port 1880 (http://127.0.0.1:1880) and you should have the Node-RED UI in front on you.