cd ~\.node-red
npm install node-red-contrib-ui

Open your node-red instance and you should have UI nodes available at the bottom. The UI interface is available at http://localhost:1880/ui (if default node-red settings are used)

cd ~\.node-red\node-modules
git clone https://github.com/andrei-tatar/node-red-contrib-ui.git
cd node-red-contrib-ui
npm install

The plugin uses the dist folder if it exists and contains an index.html file. Make sure to delete it if you want to use the non-minified version.