Default Help with multi rom


I've posted this query many times on the noom friendly thread but I havent received any proper response that is why I'm starting this thread. I've GS3 4.3 with Android HD Revolution ROM and Googi Max Kernel 2.3. As the S Tweaks has an option for dual boot, I'd like to know how to Instal another ROM on the same device. My primary rom is Android HD Revolution and I want to flash CM11 as another ROM. How do I go about this. Please help.