On machine to log in from: Generate public and private keys:

ssh-keygen -t rsa

Copy public key to machine to log in to:

scp ~/.ssh/id_rsa.pub destination_machine.domain:.

Remote login to the destination machine using password:

ssh destination_machine.domain

On the remote host:

Create authorized_keys2 in the .ssh directory if it doesn't exist:

cd ~/.ssh touch authorized_keys2

Make sure it is readable only by you

chmod 600 authorized_keys2

Append the public key to the authorized_keys2 file

cat ~/id_rsa.pub » authorized_keys2

That should be enough. Log in again from the machine where you generated the private and public keys. You shouldn't be asked for a password.