Splash page you can find : Example Theme Facebook: |

themes/facebook/plugins/default/pages/contents/index.php

you can make changes there, remember: the header is again in a different folder for css or js: |

Header : themes/facebook/plugins/default/theme/page/elements

Have a look at my place: https://triff-oelsnitz.de/

Ok, I'm getting it now.... it is confusing but there is order in there.
Thanks Joey

Thanks David,
I didn't realize your theme was based off of the GoBlue theme.
The file to edit in that case is (outside) the themes directory in the "locale" folder.
Inside there, you will also see "ossn.en.php".
(I know its confusing, but GoBlue is the only theme I have encountered that does that, sorry).

Thanks again Joey. I've got a new theme now. But I think I'm in the wrong place:

./newtheme/locale/ossn.en.php contains only

<?php
/**
* Open Source Social Network
*
* @package (openteknik.com).ossn
* @author OSSN Core Team <[email protected]>
* @copyright (C) OpenTeknik LLC
* @license Open Source Social Network License (OSSN LICENSE) http://www.opensource-socialnetwork.org/licence
* @link https://www.opensource-socialnetwork.org/
*/
$en = array(
'goblue:settings' => 'GoBlue',
'admin:theme:goblue' => 'GoBlue',
'theme:goblue:logo:site' => 'Site Logo',
'theme:goblue:logo:admin' => 'Admin Logo',
'theme:goblue:logo:large' => 'Logo file is too large!',
'theme:goblue:logo:failed' => 'Logo upload failed',
'theme:goblue:logo:changed' => 'Logo has been changed.',
'theme:goblue:browercache' => 'In case images does not appear. Please clear your web browser cache to make the images appear'
);
ossn_register_languages('en', $en);

Inside your theme folder is a folder called "locale" and inside that folder is a file called "ossn.en.php".
Edit the ossn.en.php file with your favorite text editor to replace the "Welcome to" message and "Make new friends, etc." with whatever you like.

Once you become more familiar with the way things are inside OSSN, you need to learn how to make your own theme and only make changes to your custom theme. The reason is, whenever you update your OSSN to the latest version, you will lose all your customizations unless you learn to create your own theme.
Its really very simple...
https://www.opensource-socialnetwork.org/wiki/view/1063/how-to-develop-a-new-theme