The default options are currently selected, so just press the configure button at the bottom to use them. If you want to change them, though, it is important that you read the readme.html file, since it explains what each setting does.
Required Settings:
Optional Settings:
Language Settings:
When you press Configure, the script will attempt to write the config data to the file. If it cannot (for example if it does not have write permission in the directory) the config file will be downloaded, and you will have to upload it to your server. (It should be named AutoIndex.conf.php and put in the same folder as index.php)