By default your main website is loaded from the public_html folder of your account. The public_html directory is also called web root folder or document root folder. 

If your would like to keep your site's files in a sub folder of the public_html, and do not want the sub folder to appear as a part of the URL to your website, you can mask the sub folder from the URL by placing the following directives in the .htaccess file inside the public_html folder:

RewriteEngine on
RewriteCond %{HTTP_HOST} ^domain-name.com$ [NC,OR]
RewriteCond %{HTTP_HOST} ^www.domain-name.com$
RewriteCond %{REQUEST_URI} !folder/
RewriteRule (.*) /folder/$1 [L]

In the above lines you should replace the following:

domain-name.com - Type your own domain name
folder - Type the name of the sub-folder which has the test/development website

If there is no .htaccess file in the public_html folder you can easily create one using cPanel->File Manager. 

Then, type your domain name in a browser and you should see the website which is in your sub folder.