To change your withdrawal address please follow the below steps:
(If you have locked your address you will have to unlock before changing to a new address, this will take 24 hours for security reasons)
1) Enter "settings" menu
2) Click on either Bitcoin or Bitcoin Cash at the top of the withdrawal box
3) Enter the new BTC or BCH withdrawal address you want set
4) If 2fa is set then enter your Google Authenticator 6 digit code (OTP)
5) Last step is to click on "change address" and your new withdrawal address will be set.