そーいやmacで使ってなかったので一応メモ。

cd ~/.ssh
ssh-keygen -t rsa -C "user@hogehoge.com"
Generating public/private rsa key pair.
Enter file in which to save the key (/var/root/.ssh/id_rsa): 
Enter passphrase (empty for no passphrase): 
Enter same passphrase again: 
Your identification has been saved in /var/root/.ssh/id_rsa.
Your public key has been saved in /var/root/.ssh/id_rsa.pub.

以下のコマンドで内容をメモる。

vi id_rsa.pub

Account Settingsのキーの方にペーストする。

ssh -T git@github.com
Hi hogehoge! You've successfully authenticated, but GitHub does not provide shell access.