Why you need to add a bank account you?  Adding a bank account tells  parents and guardians where you want to get paid. adding a bank account is mandatory so that as soon as parents or guardians can make payments as soon as they want to. As a school owner you can choose to have more than one bank account where different payment items are to be paid into but the first bank account you add would be your default bank account.  
You would have been required to add a bank account when you initially signed in  which will be your primary bank account.

To add another bank account do the following:
1. Go to setup >> payment setup >> bank accounts 
2. Click new bank account button.
3. Input bank name.
4. Input account number.
5. Input account name.
6. Click on the "Save" button.