Thanks Birdoasis,

I've done that already. I've edited the following files for my various issues:

1. Meta Tag & title Edit:
includes/languages/english/Posh by Trois Soeurs/meta_tags.php

2. Copyright Edit:
includes/languages/Posh by Trois Soeurs/english.php

3. "TagLine Here"
includes/languages/english/Posh by Trois Soeurs/header.php

4. "Congratulations!..." Edit
includes/languages/english/Posh by Trois Soeurs/index.php

 5. "Main Page Sample Text ..." Edit
includes/languages/english/html_includes/Posh by Trois Soeurs/define_main_page.php

I also deleted the text from the Define Pages Editor in the Admin but every time I go back to it the text is still there.

I pretty sure I've done everything correctly, that's why I'm so confused!