Launching Power App Form from Document Library

Hi,

I am trying to launch the Power App from clicking on an Item in the Document Library. I don't know how to get it to work.

This is what I have done so far.

I have created a Document Library 

In the Library settings -> Form Settings I have Selected PowerApps

I have created a Customize Form

When I click on the Document Icon it launches the Document (i.e. Word, excel, Picture etc). How do I get it to open my PowerApp Form instead?

thanks