To Create One Page Navigation in Denzel theme, first, You have to go to Appearance > Menu to create a menu.

After clicking on menu, You will redirect a page to create a menu. Hit create a new menu link. Give a name for your newly creating menu and hit on Create Menu button.

Now your menu name has been created successfully. Now you have to add some custom links to linking menu with section to section. Click on Custom Links tab. After clicking on Custom Links tab, a box will open like below screenshot.

Put your URL Link and Menu Text and hit on Add to Menu button. Don’t forget to put a hash(#) tag before URL Link.

Then, Check the One Page option and Hit on Save Menu button

Now You successfully created your newly menu with link. You can add more custom links just click on add to menu button.