Use the instance of this in the plugins array of the webpack config.

Example
const WorkboxBuildWebpackPlugin = require('workbox-webpack-plugin');
.
.
module.exports = {
  entry: {
    app: './step1/app.js'
  },
  output: {
    path: __dirname + '/step1/public/js',
    publicPath: '/public/js/',
    filename: '[name].js',
  },
  plugins: [
   new WorkboxBuildWebpackPlugin({
     globPatterns: ['**\/*.{html,js,css}'],
     globIgnores: ['admin.html'],
     swSrc: './src/sw.js',
     swDest: './build/sw.js',
    });
  ]
}

Classes

WorkboxBuildWebpackPlugin