If you have been assigned as an authoriser to a form, you will have the ability to approve or reject the submitted form.
From Home, select Forms.
In the Submissions tab, select All Categories.
Tap on the Filter icon.
The Filter page will appear.
Tap on the checkbox inline with Pending my approval, and Apply.
All the pending forms that require you to authorise will be listed.
Select the form you with to authorise.
You will have the options to Approve or Reject the form.
Tap Reject.
A reason for rejection prompt will appear.
Type in the reason and tap Reject.
After rejecting the form, the status will be changed from Pending to Draft.

Click here to learn how to approve a form.