Make sure that Iterations are enabled in your Workspace.
Navigate to the Iterations page from the navigation bar.
To edit an Iteration, click on an Iteration from the Iterations page to access the Iteration detail page. From here, edit the title or description by clicking the respective buttons. Edit the start and end dates by clicking the dates field in the right sidebar.
To delete an Iteration, navigate back to the Iterations page. Click the contextual menu next to the Iteration title and select Delete Iteration.