To update any of your submitted details, please head over to the Profile tab by pressing on your image at the top right corner. From here you will Preferences, Account, Bank & Payment, Notifications & Get help.
In each category, you will see tabs regarding your tradelink, bank account, etc. Press on the tab you are looking for, and you are now ready to update your details ✍️
Please note: Your cannot link a new Steam account to your account on GamerPay. If you switch bank accounts, you will have to submit a new bank account statement 🏦