If you didn't add your payment details when you signed up, or if you want to change it, you must send a support ticket to update it. Once you add the information, it will stay, so you only have to do it once (unless you change it with another ticket later).
To change payment options, simply use the "Payment Type" dropdown list in your Account settings and select which one you want to use. If all the necessary information is filled in, you will get paid as usual.
To hold the commissions in your account, simply set the "Payment Type" dropdown list to "Save commissions in account". That way we know not to send your money anywhere.
Please see this Help page article for detailed info and instructions about the different payout systems.
If you want to get your payouts directly to your bank account with TransferWise:
If you want to get payout in Bitcoin:
If you want to get your payouts to Paypal:
You can see what information is currently registered with your account on the "Our info about you" page under the Account tab.