public key authentication

hi, im new to winscp and just installed it today. I want to connect using public key authentication.I've generated the dsa key, copy-paste the key to the server, save the private key, but i always got this error.

Authentication log (see session log for details):
Using username "xyz".
Server refused our key
No supported authentication methods left to try!

Connection has been unexpectedly closed. Server sent command exit status 0.

please help.
thank you very much.

Only hint I can give you is that you have pasted the public key to wrong file. You may also try other SSH client (like Putty) to verify that.