how to setup ssh public key based authentication

[Guest]

[actaris]

Hi,
as in subject.
I need to use only public key and  deselect the password based authentication.
I followed this how to: http://www.howtoforge.com/how-to-configure-ssh-keys-authentication-with-putty-and-linux-server-in-5-quick-steps but:
1 the adduser command doesn't works in endian.
2 where ( in wich file ) i can put the rsa key? In /root/.ssh/? and in id_rsa? or authorized_keys?
Any idea?
tnx