First of all you need to enable the Name & Number module in mainBarModules to display the module in the navigation.

var $fpd = ('#your-designer');
var pluginOpts = {
  productsJSON: 'json/designs.json',
  designsJSON: 'json/products.json',
  stageWidth: 1200,
  stageHeight: 800,
  mainBarModules: ['names-numbers', 'drawing', 'products'], //display Names & Numbers module in first position of navigation
  namesNumbersDropdown: ['S', 'M', 'L', 'XL'], //optional: define dropdown values, e.g. different sizes
  namesNumbersEntryPrice: 10 //optional, define a price for every entry 
  var yourDesigner = new FancyProductDesigner($fpd, pluginOpts);

To enable an initial text element as placeholder for a number or name (text), you need to enable the numberPlaceholder or textPlaceholder property in the text parameters