PIN Code is used as an additional security layer for cryptocurrency withdrawal requests. You can set personal PIN Code with 6 digits at Security > PIN Code on BtcTurk | Kripto.
The PIN Code you created will be asked to create cryptocurrency withdrawal requests. If you enter your PIN Code incorrectly for 5 times, your account will be locked for cryptocurrency withdrawals for your security. You'll have to send an unblock request to support@btcturk.com from your registered e-mail address in order to be able to withdraw cryptocurrencies again.