Default [Q] Following Instructions

I want to know when you say "install ROM' exactlty what do you mean? I have rooted the phone, installed all the drivers, installed ROM manager, done a factory wipe, opened the recovery programme. the phone cannot see the file no matter where I put the ROM. Can you inform me as mentioned earlier exactly where and how do you install the Optimus G3 ROM?
The ROM has been downloaded to my desktop, extracted and ready to go, but go where that is the question.
I have entered the recovery mode and that goes nowhere unless I want to wipe/factory reset again, it would be nice if I knew where the ROM was to be placed in order that my phone can see it and install it.

Thank you.

Is there an actual step-by-step set of instructions, various sites give differing instructions and most of them are incomplete?