If you want to change your SMF application's index page title you will have to edit the following file:

~/SMF_installation_directory/Themes/default/languages/index.LANGUAGE.php

where LANGUAGE is the current language which your application is using.

You will have to find the following line:

$txt[18] = $context['forum_name'] . ' - Index';

and change the value of the forum name variable to the desired title.

After the change your new title should appear on your SMF home page.