What the message means is that you must have a 64bit operating system. See: System requirements for Photoshop Lightroom for Mac and Windows OS
To use Lightroom you will need to upgrade Windows to a 64bit rather than 32bit OS.
Lightroom 6 can only be run on 64-bit operating systems. Based on the error message you are receiving, apparently you have a 32-bit operating system. You'll have to check to see if your computer can handle a 64-bit operating system. If it can, then you need to install a new operating system.