To add Approval Workflow to any task, open the Advanced Options of your task.
Scroll to the Requires Approval By field. Select who the task is assigned and who must approve the task.
Once the task is finished by the assignee, the approver will be notified to approve the task.
All tasks that need approval will show up in the Pending Approval part of the Dashboard. Click to approve the task or to deny.
Once approved or denied, click the task to go to the content. You can then leave a comment inside of the content to give more information on why it was approved or denied.