On Mac OSX, the native SSH client can use the built-in keychain directly. To add your private key to the keychain simply use the command:
ssh-add -K /path/of/private/key
As an example if your private key is stored at ~/.ssh and is named id_rsa, you would use the command:
ssh-add -K ~/.ssh/id_rsa
You will then be prompted for your passcode, which will be stored in your keychain. After this you should be ready for a password-less login.
Source: https://wiki.hpcc.msu.edu/display/hpccdocs/Adding+a+Private+Key+to+Your+Mac+OSX+Keychain