First run ...
ssh-keygen -t rsa -b 4096 -C '[email protected]'... from terminal, then run ...
eval "$(ssh-agent -s)"... then run ...
ssh-add ~/.ssh/id_rsathen copy the content of ~/.ssh/id_rsa.pub and add it to github under Settings >> SSH and GPG keys >> New SSH key,
then run ...
ssh -T [email protected]and confirm!