How is the status of the meeting minutes updated?

I see different things under status for the meeting?  One is NEW, another is CLOSED, and another is APPROVED.   

How is the status changed or updated? 

When a meeting is created it will have a status of NEW.

The status changes from New to Closed when you close the meeting (assuming that the meeting has been called to order earlier).

How do I change the status to Approved?

The meeting must first be closed. In a subsequent meeting, add the past minutes' module to the agenda. Then approve the motion. The minutes are converted to pdf and can't be further edited.  

Meetings can be re-opened by going to adjournment and clicking on the Open Meeting button (see screenshot below).