GitHub登录窗口未显示

Question

未显示要登录的GitHub窗口。

我按照本教程https://www.youtube.com/watch?v=SWYqp7iY_Tc的每一步进行操作，但是在28:25分钟时，没有显示GitHub登录窗口，而是收到一条消息，提示：

$ git push -u origin master
git@github.com: Permission denied (publickey).
fatal: Could not read from remote repository.

Please make sure you have the correct access rights
and the repository exists.

有人可以帮我吗？