I wrestled with this myself. All the videos, instructions, etc say modify that part of the settings.php but when I looked in sites/default/settings.php all I found was a bunch of "*" and lots of directions. In that code there was the
if( !isset($databases) )
$databases = array();
$databases['default']['default'] = array(
'driver' => 'mysql',
'database' => 'databasename',
'username' => 'drupaluser',
'password' => '',
'host' => '127.0.0.1',
'port' => 33066 );
I think there is a line for "prefix" as well.
What I found was that in the sites/devdesktop/site-name/sites/ directory is a shortcut (I think that is what the little arrow means) which includes a file called "settings.php". THIS settings.php had the non-astericked code lines defining database and user as highlighted in every video tutorial and directions that I read.
After modifying this settings.php, i was able to get my site (partly) working. The other part is dealing with the .htaccess file(s) of which I have not completely fixed.
Wanted to share this as it may help someone / prevent someone from searching for the proper settings.php using aquia devdesktop.
Certainly a bit of a pain - but it seems that acquia is adding their own customization to the core drupal setup so to make it very easy for you to use THEIR cloud services, and certainly made if very difficult for me to figure out what needed to be changed for my site to Godaddy.