Managing a custom Scalar install with local_settings.php
<scalar root folder>/system/application/config/local_settings.php
You can open this file in your FTP client, or download to your computer, edit, and overwrite back to the server. Comments in the file will describe what each config item controls. If, for example, you wish to have a Scalar registration key for your Scalar install so that folks need the key in order to register new accounts, you would change this:
// Register key (leave blank if no register key required, e.g., array())
// One of the strings placed in this array will be required in order for new users to register
$config['register_key'] = array();
... to this:
// Register key (leave blank if no register key required, e.g., array())
// One of the strings placed in this array will be required in order for new users to register
$config['register_key'] = array('my key');
Another practical example is the Google Maps API key. This key will need to be present for Scalar's Google Maps Layout and Widget to work, otherwise you'll get an error message from Google when loading a page in that layout or widget. You can acquire your own API key about halfway down on Google's Google Maps APIs page.