The plan view shows dates from left to right along the top and tasks from top to bottom on the left.
Tasks wihout a start and end date won't appear in the Plan View, but still shown in Board View.
As you hover over the planning canvas, you will notice the corresponding coordinates for the Task its duration.
Redefine the Start and End DateThe Plan View lets you redefine a task's start and end date. You can drag and drop the block on the canvas that represents a task in the timeline. You can extend the duration by clicking at either end of the block and dragging to extend.
Continue to do this for each of the Tasks to plan out your project.