Build the source using elm-make in the src directory
$ elm-make Presti.elm
We also need the file glue.js. This can be generated by executing glue.js.sh.
$ bash js/glue.js.sh
This script assumes you have a variable BACKEND_URL in your environment. This will be added to the .js source in the appropriate places. I did it this way because I don't know of a better way to make the backend URL configurable in a Docker container.
After that, just open index.html in your browser!