1. If you have 'Manage' permissions for actions, you can access the web dashboard and mark actions as complete from here. as shown below:
2. You can edit an action and set an end date for the action. Also, it is possible to eliminate the action if it is no longer required.
Once the user accepts the action assigned to him, then the action will be moved to my actions. The user clicks on his action for details, there is a button to mark it as complete. After clicking on it, you can choose to add evidence by clicking picture or attaching from gallery.
Choose the media and click on 'DONE'.