Extension:GettingStarted

The GettingStarted extension adds a Special:GettingStarted page to assist in introducing new editors to the project.

Customization
The Special:GettingStarted page is shown to new users immediately after the account creation process completes. You can customize the gettingstarted-msg message by editing the MediaWiki:Gettingstarted-msg system page to change what will be displayed to the user on that special page. The Special:GettingStarted page also be linked, and visited at any time.

Do take a look at the English Wikipedia's example on how the message is customized, and how the output will be.