Tasks can be triggered manually in the Admin app, by cliking on the Tasks tile. All task templates are displayed. Select the task template for which you want to trigger a task manually and click
the icon (1). Select from the menu "Trigger manually" (2).
A dialog will popup where you can select the assignee and expected start date & time and end date & time.
By pressing the "OK" button the task will be created.
See also the article 'How do I work with machine tasks?'