The navigation bar displays the audio cursor and the selection as numbers, and lets you edit them. Values are displayed in the current time format. The selection is normally shown as a starting and ending position, but it can also be shown as a starting position and a length, by pressing the Show Length button at the far right of the navigation bar.
To modify a value, left-click in its edit box, edit the existing value or type a new one, and press Enter or Tab. Once the navigation bar has focus, you can switch between its edit boxes via Tab and Shift+Tab. You can also use F6 to toggle between the view and the navigation bar. To show or hide the bar, use View/More Bars/Navigation Bar.