You can book time directly on your tasks. Every task is attached to a project, so the timestamp will be created for the project and the task.
In order to start tracking the time on a taks, click on the "Play" button in your task list.
The task and the timestamp appear in your timestamp list as running. In order to see the column "Task", right click on the column header and choose to display the column "Tasks".
To run a report about the task you should group your timestamp list by tasks.
If you open the task, you can also see the logged time on the task if you switch to the tab "Times".