To send a payment with RentTrack using your bank account, you'll need to know your routing and account number.
The easiest place to find them is on any check from your checkbook. They are right at the bottom:
If you don't have a check book, you should be able to find your routing and account number somewhere inside your online bank account. Try checking in the "account information" section.
You can also try looking on the monthly statement you receive in the mail for your account number.
Here are a few helpful articles on how you can do this with a few major banks: