I am helping a friend who has a site self-hosted via Wordpress. They have access to their FTP. Now I am familiar with manually updating files through the FTP and that is how I usually update my sites. (Because I deal with mostly static sites).
The question, how can I upload the new coded site to be the www.example.com to show instead of the current website? Can I redirect the index.php of the current site to go to the new code?