Hello,
PS3 without additional mods can only read Fat32 formatted external data devices. To add NTFS compatibility you need to install "prepNTFS" program, can be found on search engines pretty easy.
To make webamn, multiman automatically scan games from external NTFS HDD, in root folder of the external device you need to create "PS3ISO" folder, and put .iso files in this folder. For other medias: /PSXISO, /DVDISO, /BDISO.
"prepNTFS" is a PKG file, simple to install.