All hosting accounts in SigmaWeb permit uploading through FTP, File Manager and other web development programs. Use Cpanel > File Manager as the easiest way to upload files on  public_html directory. 
Index page must always be named as index.html, index.htm, index.php etc.


As an alternative, you can use an ftp program. We suggest FileZilla which you can free download at http://filezilla-project.org/download.php . Take into consideration useful advice for setting issues here.