How to personnalize popup push web ?

How to personnalize popup push web ?

Hello, 

I have activate the push notifications in my website in two step, and I would like more custom the popup : 
  1. Change the content to add more text (the size of the fields is very to small )
  2. To remove the "Powered by Zoho"  You don't pay your ads in my web site, but I pay a subscription to Zoho 
  3. To change the css of the iframe page for a better integration with the style of my website

Are you an ideas for modify this ?