Setting up the Financial Defaults is done under Admin / Defaults / Manage Financial Defaults.
This generally is done during the setting up of your system, particularly for the first five sections below.
Some areas may be added to later, particularly the bottom four sections. It is okay to have these as being blank if they are not used.
Please note that if you make any changes to these Defaults they take effect from the date of the change only. They are not backdated.