Go to Site Info.
Select the Site Info tool from the Tool Menu of your site.
Select Manage Tools.
Select Manage Tools from the Actions Menu.
Check the box to enable subpage navigation.
Below the list of currently-added tools on the right, check the checkbox Enable sub page navigation in the left tool menu.
Select Continue.
Scroll to the bottom of the page and select Continue.
Subpages display in Tool Menu.
You may now select the top-level Lessons page in the Tool Menu to display its subpages as links in the menu.
Note: Only one level of subpage will be added to the menu, regardless of how many additional pages are nested within those subpages.