To setup your Runescape bank pin you need to speak with a banker in a Runescape bank and select your bank settings to set your PIN. We you are creating a new bank pin you need to enter your new PIN twice to confirm that it is the pin you want. After you have set your pin there is a 7 day waiting period before the pin will take effect which essentially just put in a safe guard in case someone hacks your Runescape account and attempts to put a pin on your account.