I want to install and costumize all the site in another domain then to deloy it

Hello, hope you are good and work is going well,

I just purchased the theme to you.
I want to install and configure all the site in another test domain for development and then to deploy it in real world domain that i want to have it.
I want this because of my old site is still up and running so i dont want to take it down now.
I want to make all the site ready then to upload the new one.

Can you please let me know how can i do this ?

Ticket