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The latest version of Play Memories requires Mac OS X 10.8 or latest version. So you need to upgrade your Mac OS X 10.6.8 to latest version first to install latest Play Memories. You can download the latest 10.11 El Capitan upgrade from App Store.
or from here --> https://itunes.apple.com/in/app/os-x-el-capitan/id1018109117?mt=12
However there is an older version (version 1) that works with Snow Leopard 10.6.8 if you don't want to upgrade to latest version of OS X. You can download it from here --> http://pmb.update.sony.net/PMH/qgUFH7M9xy/PMHOME_1000DL.dmg
I also found version 2, get it from here --> http://pmb.update.sony.net/PMH/YHfLesPEMY/PMHOME_2300DL.dmg
If you have any questions or would like any additional information, please don't hesitate to ask.