By default your 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 you've created a test website under a sub-folder and you want it to be displayed when you type your domain name, add the following lines to the .htaccess file in the public_htmlfolder:
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 2 strings:
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 test folder.