After you added a task to the plan you can easily reassign or reschedule it using a simple drag&drop.
If you don’t know how to add tasks, follow this guide: Add tasks
Locate the task you want to edit all then hover over it and grab it with the left mouse button. While you hold the button the task will follow you and you can drop it to any other user and day. The place the task will end up will be highlighted.
If you want to change the duration of the task, for example, make it 2 days long instead of 1, than do the following actions:
Hover over the task.
Grab one of the icons that showed up.
Move the mouse over the desired day while holding the left mouse button.
Let go of the left mouse button when you reach the desired day.
The task duration should be changed now.
