To cash out your casino bonus, you will typically need to complete certain requirements set by the casino, such as fulfilling the wagering or playthrough requirements. These requirements usually require you to wager a certain multiple of the bonus amount before you can withdraw it.
You just have to stick to legal, regulated online casino sites such as BetMGM, Caesars Palace Online Casino, FanDuel, Betway, bet365 and BetRivers. They offer great casino game ranges and they will pay out quickly and without any issues if you win.