Creating a new rig?

I've seen the details of what to do to get a specific sound. But my question is really even simpler than that:

How do you create a new rig from scratch? Like what knobs to you turn to even add a simple rig?

easiest to start with a decent preset and just change the things that you want to change. pick any factory preset for example and change the amp model to a different one and then try a different cabinet. tweak the settings until you like what you hear. that's the basics of it.

Right, but how do you name it (eg. "Big Swamp") and assign it a number (eg. B7, Z3 )?