Here is how you can accomplish this without interruption.
To install Wordpress, we recommend using the automatic install method from the Application Tab within the Customer Control Panel
Once logged in, click the "Application" Tab > Click Wordpress > Select the domain > Click Install.
During the installation process you will be asked to enter a "URL Path". This "Path" is a virtual directory that redirects the user to the Wordpress application.
For example the URL Path might be /demo which means you can only access the Wordpress site via http://your-domain-name/demo.
Now you can develop your Wordpress site.
When you are ready to replace the live site with the new Wordpress site you will need to change the URL Path from /demo to just “/” without quotes.
Here are the steps to do that.
Log into the Customer Control Panel
Click on the "Applications" tab. Click on Wordpress, then click on your domain where you've installed Wordpress.
Scroll to the bottom of the page, you'll see a "Change URL Path" button, click the button and remove the word demo and keep the slash "/" there, then click "Save".
This will update the root location for the domain in question to point to the Wordpress installation.
Please note this change may require you to update links within the site that maybe still referencing the URL with /demo associated with it.
There are many useful plugins that can help in this area, one example is a Wordpress Plugin called Velvet Blues Update URLs which allows you to easily change one URL to another.
Congratulations you have successfully installed and developed a new Wordpress site and replaced your existing website with just a few clicks.