string templates are not supported by current javascript version

I am trying to use ES6 String Templates in a Node.js (v 5.7.0) app, but they are not working. Webstorm is correctly warning me that

String templates are not supported by current Javascript version

I am sure I have used string templates in a node app in the past. How can I get string templates to work? I am running the server with this command

npm start

When that is fixed, how can I help Webstorm know it is fixed and stop showing the warning?

Edit: I changed the app source to use template strings in this manner:

`````

var app = express();
var server = app.listen(process.env.PORT || 8080, function () {
    var host = server.address().address;
    var port = server.address().port;
    console.log(`App listening at http://${host}:${port}`);

`````

the app prints:

App listening at http://:::8080