Follow below steps to set up web push ID : 
  • For this, you need to first login to the Apple Developer Console. Here, we are going to create a unique Website Push ID for push notifications.
  • In the Developer Console, on the leftside pane click on  "Certificates, Identifiers & Profiles". On this certificates page, click on "Website Push IDs" on the left and press the "+" sign to create a new Website Push ID.
 
  • Enter a description and identifier. The identifier follows reverse-domain name styling. So you should enter something like "web.com.pushflew.example". (Note: "web" is added automatically to the identifier). Press "Continue" to proceed.

 

  • Verify the details (Name and Identifier) you entered. Click on "Register" to proceed.

 

  • Click on "DONE" on the next page. You should be able to see a Website Push Id created in the list now, as in the below screenshot :

 

Next step : Generating Web Push Certificate.