Bonus Cash is used to enter cash tournaments, exactly like regularly deposited cash, and is automatically paid as part of your entry fee.
If both Bonus Cash and Withdrawable Cash are available in your balance, it is important to note that up to 20% of the entry fee will be paid in Bonus Cash upon entering a tournament, and the rest will be paid in Withdrawable Cash. For example, a $1 entry fee would cost $0.20 Bonus Cash and $0.80 Withdrawable Cash to enter. This cost is automatically deducted from your balance upon entering the tournament.
When Bonus Cash is used to enter a tournament, any winnings on top of the Bonus Cash amount used to enter are converted to Withdrawable Cash. For example, if you enter a tournament with $1.00 USD as the entry fee using Bonus Cash only, and win a prize of $2 USD, $1 USD will be given back as Bonus Cash, and the remaining $1 as Withdrawable Cash.