There are two methods are available First is to use a third party FTP software like smart FTP , Filezilla etc . Use this with Cpanel or plesk [ Best method ]
or you can use the following method without any FTP Software
Steps to follow
1) type ftp://<your domain>/ in your internet explorer address bar in windows 7 /XP/Windows 8
2) when it asks username and password just put username and password
3) then you see a folder " FTP root at your domain"
4) From the PAGE option in right top on your browser select " Open FTP site on windows explorer " in bottom of the page menu in IE ( if any security messages appear just click allow)
then put again username and password when it asks
then open httpdoc / public html
copy and paste files into that folder just as copying the files in a system.
Just copy and paste file into the remote folder