OpenSSH is supplied with Macintosh OS X and runs much like it does for other Unix-like operating systems. The primary differences and distinguishing features are:
Some extra setup before the OpenSSH server, sshd, can be accessed by the outside world
The software, which is a modified version of OpenSSH maintained by Apple
Some important differences in the way sshd is configured by default, such as invocation and Kerberos support
The usual OpenSSH clients, ssh, scp, and sftp, work normally without any extra effort on your part:
# Log into server.example.com as user smith
$ ssh -l smith server.example.com
# Copy myfile from your local machine to server.example.com
$ scp myfile server.example.com:
# Run an interactive file-copy session with sftp
$ sftp server.example.com