Hi Kundan,
The burndown chart is visible in the teams area of Workfront when the team is set up as an Agile Scrum team and an iteration is in flight.
Burndown charts are designed to visually represent how your work is progressing through an iteration, it shows what work is left to do vs time left within current iteration (note that a burndown chart will not appear for kanban teams as iterations are not traditionally used kanban methodology). If you have teams who use scrum, you will need to set them up as a scrum team within workfront and once they have planned an iteration into the system and added their stories from the backlog, a burndown chart will appear for the current iteration.
Best Regards,
Rich.