You can easily add a task by using the green “Add task” button in the top right of the page.
If you are on a rush just enter the Task name and click “play”. You will start tracking time by then.
If you click the confirm button you can start the timer at any time. Right next to the task progress bar you'll find the task timer. At the top of the screen there is the main timer were you can start thetimer for the last task you've been working on.