Install Violentmonkey
To install Violentmonkey, go here :
https://addons.opera.com/fr/extensions/details/violent-monkey
Then click on Add to Opera

---

Install A4A801
To install A4A801, go here :
http://outil.derpolino.shost.ca/addon/A4A801.user.js
A window will open, click on Confirm Installation

---

A4A801 is now installed!