First to be given away is free DLC for Assassin’s Creed Valhalla. This Rewards pack consists of the Seafarer Settlement Pack, and an outfit resembling Bayek from Assassin’s Creed Origins. These free DLC are available for all platforms, so there’s no reason to choose not to claim them.
Though when you do claim them, you don’t necessarily get them immediately. Once you visit the dedicated giveaway page while signed in, the site tells you that your Rewards pack “will await you directly in your game inventory within the next seven days”. Ubisoft will also let you know when it happens with an email. (Source: Ubisoft [1], [2])