Permission denied (publickey). fatal: The remote end hung up unexpectedly

 I have followed these instructions below to upload a project.

Global setup:

 Download and install Git

  git config --global user.name "Your Name"
  git config --global user.email chandra@gmail.com
  Add your public key
Next steps:
  mkdir chandrarfio
  cd chandrarfio
  git init
  touch README
  git add README
  git commit -m 'first commit'
  git remote add origin git@github.com:chandra/devops.git
  git push origin master
But I get this error:

Permission denied (publickey). fatal: The remote end hung up unexpectedly