Setting up OneSignal Web Push notification

While integrating OneSignal Web Push Notifications in a Web App developed recently we followed the below mentioned steps:

• Login & Create New App in OneSignal
• Follow the steps mentioned here for quick setup
• Select Platform Web Push
• Configure the new Web Push app

Important points that are not clear from the documentation are:

• Placing the Web Service worker files, which need to go into root dir
• Sending individual notifications, this guide provides resolution to this issue.