To create an FTP account, log into your cpanel at:
http://yourdomain.com/cpanel
Once logged in, click on the FTP accounts icon.
From there, you can follow the steps in this cpanel documentation: http://docs.cpanel.net/twiki/bin/view/AllDocumentation/CpanelDocs/FTPAccounts
There is also a video available here: http://www.cpanel.net/media/tutorials/ftpacct.htm