Make sure its formatted in FAT32 and all you need is a GAMEZ folder with your games inside. you can just connect your hard drive to your pc and copy/paste any game with NO files larger then 4GB. for games that have files larger than 4GB you have to FTP them to your PS3 and then copy them to your external using Open Manager.
This will automatically split the large files so they can be stored on your external drive. you cannot play games with files over 4GB from your external you must first copy them over to your PS3 with Open Manager in order to play them