Task board is an important tool in the Agile process. It helps the team to focus on the work at hand in the current sprint and feed progress data back into the system.
The Task Board is not a sprint-planning tool; it is more of a sprint-tracking tool. Use the Planning Board for planning the stories that will be dealt-with in the sprint. During the sprint, team members can use the Task Board to break down the stories into tasks and track them to completion.
For more information, see What are Planning and Task Boards?