Can someone Explain like I'm 5 how the Hearthstone’s 10-Year Anniversary event works?

[Silverleigh-drakthul]

Hoops for Fiery Hearthstone Mounts?

So I just restarted my subscription for WOW (did not know it had been that long), logged into Hearthstone and then into World of Warcraft, checked the mainbox and… … no mount. Is there another hoop or more I am unaware of like… you have to have a certain level character on your account? Or have purchased Dragonflight? Or be opted in for something? Thank you for your time. P.S. Already have the blue Hearthstone mount so yes, there is play on my Hearthstone account.