Before redeem a Free Spins bonus, or claim any other casino bonus, read the terms and conditions attached to them. After that:
go to the ‘Cashier’ section and find the ‘Bonuses’ button there;
look for the bonus you’ve chosen, click ‘Claim/Redeem’;
insert the code word from the coupon if it’s required (‘Enter Code’ tab);
deposit the minimum amount (if needed) and start playing;
fulfil the wagering requirement: play through the casino credits that you’ve won with Free Spins;
withdraw your winnings (complying with the maximum cash-out limit if it’s there).
In the case of Free Spins with no wagering requirement, all the winnings go straight to the real-money account, ready for withdrawal.