Open the dropdown menu on the top right of the confluence page, clicking the menu item "Navigation View" will turn on the plugin. The Navigation Sidebar will appear as long as there are defined headings in the page content. Please note, the headings defined by the Selector in settings (Space Tool or Configuration) must be used in the page content.
Right Side Mode
By default the Navigation Sidebar will be displayed as a column on the right side of the page.
Click the switching button on the right of the Navigation title to switch to Popup mode.
You are able to switch the Navigation Sidebar to Popup mode so it will take no space of the page content. Only a small menu icon appears on the right side of the page. To make the Navigation Sidebar visible you just need to move your mouse on the menu icon. And it will be changed back to menu icon if your mouse left the Navigation Sidebar area.
Resize the Navigation Sidebar
You can resize the width of the Navigation Sidebar by dragging the dragging button that is close to the left side of the sidebar. In fact the whole area in red as below is draggable.