Turbo Spins are used to progress faster during specific challenges. Each action counts twice with Turbo Spins. For example, one Big Win with a Turbo Spin will be counted as two Big Wins towards your challenge progress. 

These spins are used automatically as you play, and you can see how many you have by looking at the challenge icon. If you collected free Turbo Spins, or purchased Turbo Spins and do not see your total updated, simply restart the app to have them added. If you spin before restarting, your Turbo Spins are still being used successfully, even if the widget does not display the total available.