When viewing your tickets within your Teamwork Desk account, an encircled check mark icon will show inline with the ticket. If the task is active this will show display a red check, while a completed task will display a green check.
When within the ticket itself, there is a task indicator that will give the details of the task.
From here, you can select the task name, view the ticket and update the task if necessary. Options available here would be to add a comment, change the due date, and many more.