Insert the following in your page to have the headings automatically numbered:

To extend this to the whole wiki,

• edit objects of page Macros.NumberedHeadingsStylesheetExtensionMacro
• navigate to the XWiki.StyleSheetExtension object
• choose "Use this extension" : "Always" instead of "On demand"
• Then all headings will be numbered without need of adding the {{numberedheadings/}} in each page

Sample result :

title 1

Title 2

toto

titi

hello

title