On your OSX machine you need to load your Identity file. This can be done two ways.

1. Defining the file in your ssh command ssh -i /path/to/id_file username@host Example: ssh -i /Users/jondoe/.ssh/id_rsa root@mydomain.com
2. Adding the file to your ssh-agent - ssh-add /path/to/id_file Example: ssh-add /Users/jondoe/.ssh/id_rsa

Note: If you get an ssh-agent error, enter: eval `ssh-agent` before #2