How to start working on a new wordpress site without taking down the old one.

Hey there,

I’m relatively new to everything wordpress/website design
and I need some help on where to begin working on a new website template to replace my old one (once it’s completed) and the best way to switch it over when the time comes.

Do I start up another account and just start working on the new theme I want, and then somehow switch it over later?

Or what’s the best course of action for doing something like this.

If this is not the best place to post this question, where would I go about then?