Note: You should not center or put any additional formatting on the text you format as headings. If a heading is not working properly, try using the Remove Formatting button to remove the formatting of the heading.
Go into edit mode on your workspace by clicking the "Edit" tab.
Click the "Insert" button and select the "Table of Contents" plugin from the insert menu.
Choose the number of levels of heading formatted text that the Table of Contents will display on your page. To just show the "Heading 1" text in the Table of contents, select 1 at this option, for more headings, select the corresponding number of levels. When you've made your selection, click Next.
Finally, click Insert Plugin and save the page.
Note: The plugin will appear on the page as a green box in edit mode, but once you view the page, that green box will be replaced with a Table of Contents for your page.
The Table of Contents is built around the Formatting structure that you give your pages. So, to make something in your page appear under the first level of the Table of Contents, set the text to "Heading 1". The next level will be "Heading 2," and so on. Below is a live example of the plugin so you can see how it works.