Although you can use the Gantt interface or the table view to add tasks into your project schedule, the New Task option under the Quick Create Menu menu provides the quickest way to create tasks.
You can select the start and end dates, set the Display on Dashboard flag, indicate the progress of the task or enter additional information in the custom fields on the new task form.
When you save the changes, you will see the new task directly under the header item in the Gantt chart or as the first row in the table view. You can then reorder them as required.