In ProWorkflow, a Projects Status is measured by the Work Stage field. This is a customisable field, with each available stage being tied to either an Active, Completed, or Deleted status. This is considered fundamental Project information, and as such is stored in the Details section as seen below:

Changing the Work Stage is a simple matter of clicking on the field. You will see each status and its corresponding state listed in the dropdown menu.

You are able to customise available Work Stages via the Work Stage menu in settings: