Where can I find a list of slots that are participating in the contest? This information was useful or should it be on the website?
The games are posted on the official website. Go on winz.io, Click on the Promotions tab > Drops and Wins, and read what it says:
Selected games: Wolf Gold™, Mustang Gold™, Sweet Bonanza™, John Hunter Scarab Queen™, Wild West Gold™, Bronco Spirit™, Great Rhino Megaways™, Dog House™, Release the Kraken™, Buffalo King™, Chilli Heat™, John Hunter and the Book of Tut™, Starz Megaways™, Pyramid King™, Hot to Burn™, Fruit Party™, Ultra Burn™, Drago - Jewels of Fortune™, and Street Racer™.
https://winz.io/promotions/drops-and-winsIf you want to participate, make sure that you understand the terms and conditions to avoid any surprises later on. They are posted at the bottom of the page.