If you are on a mobile device, visit the menu at the top left of the game screen, click on the free spins icon and press 'Spin' button to utilise your free spins on the eligible casino games. The unused free spins will be removed from your account along with the winnings accrued if not used within the seven days.
If you don't claim the offer at the time of your first deposit, you can do so at any time within 30 days of registering your account. Simply log in to your account, go to the Account menu, choose My Offers then click Claim Now for the relevant offer.