FTP and Filezilla problem

hi everyone!
I'm new here so i need some help. First i've installed succesfully cwp to my server and point my domains to my server. bigest porblem is how can i connect to my ftp via filezilla. i did everything before i open this topic so please give me clear answers that i can understand. (im not pro). in the user panel when i try to conenct file maneger (http://..../webftp_simple/) the system says
"Internal Server Error

The server encountered an internal error or misconfiguration and was unable to complete your request.

Please contact the server administrator at you@example.com to inform them of the time this error occurred, and the actions you performed just before this error.

More information about this error may be available in the server error log."

I've tried to change permisson via fix permission but still i cant reach ftp maneger. !!

Please soemone tell me how can i conenct my server via filezilla. (by the way my ftp server icon on the dashboard wont turn green its always says "failed")

thanx to all!!