In the bottom left hand corner, you should be able to select the ‘View’ button. After doing so, a new screen will appear entitled ‘View Options’.
Click on the heading ‘Show complete’, this will bring up a new screen where you will be able to select a ‘Thing status’ You will have three options:
Note: To always view completed Things or even allthings/open Things in a particular list, on the ‘View Options’ screen, select ‘Save default view’. (After doing so, a pop-up should appear notifying you that your viewing preferences have been saved.)