Installing Mac OS X Issue


Hi, i am a First time Mac User that uses Final Cut Pro But i know you cant install any software updates higher than 10.11 and id like to update to 10.11 but i downloaded the software from apple and it says Warning: The following Disk images could not be opened: InstallMacOSX (1).dmg and it has a reason of Not Recognized does anyone know how to fix it iim currently running 10.6.8 and would like up upgrade to 10.11