If an article contains more than three headings, a Table Of Contents (TOC) will normally be created automatically.
If, for whatever reason, a TOC isn't wanted it can be switched off by including when editing: "__NOTOC__" (that's: "underscore, underscore,N,O,T,O,C,underscore,underscore" meaning NO Table Of Contents). It is usual to put this at the top of the page, it will not show in the page.
Adding TOC manually
If "__FORCETOC__ "(2 x underscore each side) is used, then a TOC will occur before the first heading even if there are three or fewer headings.
Similarly if "__TOC__" (2 x underscore each side) is used, then a TOC will occur at the point where "__TOC__" is placed even if there are three or fewer headings. You can thus place the TOC at any point vertically or horizontally or in a table cell.
NB: "__TOC__" overrides __NOTOC__".
In a table
The table of contents can be forced into a floating table on the right hand of the screen with the code below:
More on headers & sections.