Ater logging into your Home Directory via FTP or using the cPanel File Manager you will see a list of directories.
The directory to upload your files into when using cPanel is public_html (Web Root). If you have additional domains the directories for these domains are also inside the public_html directory.
When using H-Sphere you upload your files into the directory named after your domain name.
Just to note that index.html will take preference over index.php, default.html etc. and will display instead of index.php, default.php etc.