First you will need to whitelist your bank account.
Go to Holdings - enter/find "USD" in the search bar of cryptos and you will see Deposit/Withdraw option tab on it but you will need to enter your routing bank number and all that.
Make note: Minimum to withdraw is $1000 bucks (unless that has changed)
An easier route would be to just withdraw your crypto to another exchange wallet. If you want to cash out/convert that way.