Free Spins are spins to use when playing Casino. They can be available immediately or it might be required to make a minimum deposit to activate them. Also, they might work only on specific slots. Specific requirements will be visible after clicking "More Info" in the Offers" section of your account.
You can start to play with it immediately! Any winnings will be locked together with the bonus funds until you meet the wagering requirements. You need to play your bonus amount 40 times into specific games before being able to withdraw the restricted amount.