Bet credits and bonus bets cannot be withdrawn, but they can be used to wager on other sporting markets your sportsbook has to offer. Some sportsbooks make you use your bonus funds or bet credits in one lump sum. Others, such as FanDuel, allow you to use them in as many bets as you want.
Click on the information icon next to your bonus funds. If you have fulfilled the wagering requirements for the bonus, your bonus funds should reflect in your available balance. When the progress bar hits 100%, you can convert your bonus funds to cash by clicking "Redeem Bonus."