you don't need to add a user specifically for ssh. Assuming the machine you're loggin g into has ssh server installed the command you need is
ssh -l <username> <hostname>
this will let you log in as any user on the remote machine.
If I understand you correctly, you're also asking if ssh need rsh, correct? No, it doesn't, ssh is completely independant of rsh, and a better alternative. Whenever possible, you should be using ssh.