Most testing work is managed through tasks that are part of runs. But you may be invited to complete other tasks outside of runs, including run management tasks and some issue reproduction tasks.
For these tasks, you see when they are due in the invitation before accepting the task. Once you have accepted a task, you find it in your Tasks list as In Progress.
When you have finished work on the task, click the task to open it. You see the task details.
To complete the task, select the actual time spent on the task. Optionally fill in the Notes with details about the task, such as any reasons why the task took longer than estimated. Then click Mark as done.