Place the cursor in front a heading that will be linked to from the navigation menu.
Place the cursor in front of the line "back to the top".
Insert > nvisible tags > named anchor > or Window > object > invisibles > named anchor >
Give the anchor a descriptive name (no spaces, case-sensitive) and click OK. An anchor "marker" should appear.
Highlight the matching menu item or top of page link location. Modify > property inspector > click the circle following the link field (point-to-file icon) > drag the arrow to the anchor marker or Modify > property inspector > link field > #anchorname