To manually change the status of a Submitted Form, in the Web Portal go to Forms > Submitted Forms > select the Checkbox for the submitted form for you wish to edit > select Change Status at the bottom of the screen, and you can choose from all of the status options.
Select your new status for the submitted form, then select the green Change Status button and the status will be updated.
A form status can also be changed automatically upon submission via a Form Action connected to the form template. In the Web Portal go to Forms > Existing Templates > select the three dots for the template > select the Actions option.
In the new actions dropdown options, you'll find the action for automatically modifying a form's status.