I'm not sure what you mean by defaults. Do you mean modifying the look and feel if there are any default templates to use? If that's what you mean, there isn't any additional templates provided to skin the store with currently.
The "entry" page is the index.php file. If you wanted the url for entry to be index.php, you could have an index.php page in the root of your server that will forward to the current location that the index.php is located (index.php) or you would have to reinstall all the PowerStore files in the root of your server. Basically all the files contained in the PowerStore300 directory would have to be copied to the root of your server and installed from there.