From the 'Payment' tab of your dashboard select 'Add a Payment Method'.  Select 'Bank Account (e-check)' and complete the pop-up form. 

To manually enter your bank account information, select 'Manually enter account and routing info' at the very bottom of the pop-up. Complete the form making sure that each box has a blue checkmark. Select the type of account you have, and click 'Authorize account'.