On the editing page, click the "Insert" tab in the toolbar and select "Template". A box will appear containing the accordion template. Click 'Ok' to add.
Multiple header labels paired with text will appear. Save these changes and view the page to see how each header expands and collapses to show its hidden content.
Go back to the editing page. Under "Tools" in the WYSIWYG for the text area in which you've placed the accordion, select "Source Code" to view the source for the section. You will need to edit your accordion in the source rather than in the WYSIWYG for two reasons. The styles that apply to your accordion will hide the content area in the WYSIWYG and there are ID values in the accordion that must be unique for it to function correctly. For full instructions on this, see the Adding an Accordion (source code) page.