The 'Account' section of the Runner's App has a sub-section called 'Bank accounts. This is where you can add bank accounts.
Click on that will take you to this screen, from which you can put in your bank details:
Deleting Your Account
If you wish to delete an account, you can. Click on 'Edit' in the top-right-hand corner, and a red delete symbol will appear to the left of all entered bank accounts. Press that symbol and follow the prompts to delete your bank account.