Putty Authentication on Mac OS X?
I use SSH Keychain on my Mac to manage my ssh key agent and attached keys. It runs ssh-agent, and ssh-add to manage the keys behind the scenes, but starts up when I login, stores the passphrase in OSX login keychain (you don't have to do this, though).
ssh-add and ssh-agent are the equivalent tools, which are built in. Best way is to read any tutorial for linux or os x in setting up auth with ssh, it will be the same.