Most of the configuration will be done on the Account Page Layout. You can watch this video, and/or follow the text based instructions below.
Add a Section to your Account Page, called Breadwinner - Xero Invoices. In that section, put 7 fields:
BW Account Status
Total Amount Overdue
Total Amount Due
Total Amount Invoiced
Total Amount Paid
Total Amount Credited
Total Unallocated Credit
Add another section, directly below the first one, called Breadwinner Charts. This section should be hidden (uncheck the two checkboxes for Display Section Header on:) and, most importantly, select 1-Column layout.
In that section, add the VisualForce page BreadwinnerAccountCharts.
Opportunity Page Layouts
Depending on how you use Breadwinner, you may or may not have your Invoices connected to your Opportunities through a related list on the Invoice record. Most people will not have done this. If you have done this, follow the steps above in the Account page layout for just the Invoice Related List.