If we can, can you show me how to do it.
thanks

yes , but only for some things :
what you can do :
play or copy from an external drive various media , music files , compatible format video files , jpeg photos
backup your ps3 system in case of ps3 failure or data loss , or if you swap the ps3 hard drive for a larger one you can restore your data afterwards
backup and play videos downloaded from the playstation store - they're copy protected and will only play on the system that originally purchased them

what you can't do :
download and play any games purchased from psn or downloadable content - these will only install and work from the internal hdd

the external drive must be fat32 format and to access media either place it in separate folders named VIDEO , PHOTO and MUSIC or press triangle on a controller and select show all