On the INSERT menu select From Drive, then click My Drive and select the desired folder. Select the folder and click Insert at the bottom. You can display List View or Grid View. You can insert more than one folder in the same page if you want to do that. Folder sharing must be "Public on the web - Anyone can find and view". If you have starred a folder it will not show up unless you scroll to the right and select starred. If it still doesn't appear, unstar the folder. If you do not see the files in the selected page, hover over over the area and click the pop-out icon.
When you insert a drive folder you can select either to show image thumbnails or file names. Click the folder after inserting it and click the settings icon and select either list view or grid view.