In summary, the steps are:
Assign an ID to your section under the Customize tab.
Create a menu to be used for your page that will use One Page Navigation feature.
Create a Custom Link with the URL set to
# followed by the ID you assigned to your section then add it to your menu.
Edit your page and under Page Settings, choose the menu you created.
If it's still unclear, try watching this video guide.
Hope that helps.