To access an ftp account using a web browser or windows explorer, use the following url format
ftp://user+yourdomain.com@yourdomain.com
For example, if you had set up an ftp account called 'test' and your domain name was joecool.com you could access it in a browser or in windows explorer using the following url.
ftp://test+joecool.com@yourdomain.com
from there, a login prompt should come up... enter the following information
username - test@joecool.com (format = ftpuser@domain.com)
password - the password you assigned to the ftp account.