With interactive timeline, you are able to view the entire scope of your Project while having the option to re-adjust dates as your Project progresses.
To be able to see the timeline in your project, you essentially need the task to have Start date and/or Due date.
Here's one simple way to do it:
Click on + Add Task
Fill in task name and input start date and due date
Click on check icon to save the task.
You will now see your project timeline.
Click and drag the block on the Timeline Gantt chart to change dates.
You can extend or move the Project/Task dates you have selected.
Also, you can select multiple date blocks as needed.
Changes made on the Timeline will also immediately reflect on Project and Task dates.