Since Tiki 16 Tiki integrate default parameters that are used by Twitter when fetching a page if they are missing or if you prefer to use your own for the entiere Tiki.
Consumer Key and Consumer Secret are used for integrate your Tiki and Twitter using a Twitter application.
First of all, go to the Twitter page for new applications and register your site as a new application.
As Callback URL you must give the URL for tiki-socialnetworks.php on your site. This is where users will be redirected when authorizing your app with oauth.
You also must ask for the access type Read & Write otherwise your users will not be allowed to tweet.
After registering your site, you get a consumer key and consumer secret which you must enter in the tab Social networks on the admin panel. (See image above)
To grant a group access to the social networks functionality, set the permission user can use social network integration (tiki_p_socialnetworks) for that group on the Permissions page.
This can be done via the Social networks tab on My Tiki.
By clicking on the Authorize button, the user will be redirected to the Twitter page, asking for confirmation. If the user agrees, an oauth token will be stored in the users preferences.