The Moodle guys helped me. Here is a solution just in case someone stumble upon the same problem:
You can add a text using:
$settings->add(new admin_setting_description('myparagraph1', 'This text goes in the same column of field names (column 1). You can just put here an empty string if you wish.', '<p>This text goes in column 2. You probably want to put a large text here.</p>'));
You can add a text using:
$settings->add(new admin_setting_description('myparagraph1', 'This text goes in the same column of field names (column 1). You can just put here an empty string if you wish.', '<p>This text goes in column 2. You probably want to put a large text here.</p>'));