The Desktop widget is designed to help you track time or add it manually. It's in sync with the online sidebar timer, so you can start it there and stop it in the desktop widget or vice versa.
If you click on the top left corner you can access the Options area from where you can easily access your Paymo account, Settings, About area and Log out or Quit.
In order to track time, you can click on the Play button to continue recording time for previously tracked tasks, or you can click on the + Add time button on the top right corner and select the desired project and task. You can start the stopwatch, add bulk time or interval time entries.
If the task isn't in the task list, you can easily add one once you write its name → Add New task.