Click "Documents" and "All documents" on the left menu. Then click the button "Upload documents". Add the folder with subfolders by clicking or drag and drop the folder to the box. Finish by clicking "Upload". See video:
Click "Documents" and "All documents" on the left menu. Then click the button "Upload documents". Add the folder with subfolders by clicking or drag and drop the folder to the box. Finish by clicking "Upload". See video: