This means, on your local machine, you haven’t made any SSH keys. Here’s how to fix:

• Open git bash (Use the Windows search. To find it, type «git bash») or the Mac Terminal. Pro Tip: You can use any *nix based command prompt (but not the default Windows Command Prompt!).
• Type cd ~/.ssh. This will take you to the root directory for Git (Likely C:\Users[YOUR-USER-NAME].ssh\ on Windows).
• Within the .ssh folder, there should be these two files:
  • id_rsa
  • id_rsa.pub
• These are the files that tell your computer how to communicate with GitHub, BitBucket, or any other Git-based service.
• Type ls to see a directory listing. If those two files don’t show up, proceed to the next step. NOTE: Your SSH keys must be named id_rsa and id_rsa.pub in order for Git, GitHub, and BitBucket to recognize them by default.
  • To create the SSH keys, type ssh-keygen -t rsa -C «your_email@example.com». This will create both id_rsa and id_rsa.pub files.
• Now, go and open id_rsa.pub in your favorite text editor.
• Copy the contents –exactly as it appears, with no extra spaces or lines– of id_rsa.pub and paste it into GitHub and/or BitBucket under the Account Settings > SSH Keys. NOTE: I like to give the SSH key a descriptive name, usually with the name of the workstation I’m on along with the date.
• Now that you’ve added your public key to Github and/or BitBucket, try to git push again and see if it works.