How do I make a new website when I already have one

I’m not sure where to start! I have downloaded www.remarpro.com and want to open it but it requires me to give my domain name and host before I can do that.

We already have a church website (it was not created using wordpress). I want to create an updated and completely different look to our existing but want to keep the existing site going until our committee finishes a new look to the website using wordpress.

So the question is how can I keep the existing one going, build a new one using www.remarpro.com, have our Vestry approve it, then “turn off” the old webpage and “turn on” our new one? I want to keep using our existing domain name and host.

I’m sure it’s simple but what’s the answer. Thanks.