ssh-keygen -t rsa -C "your-email-address" -f "github-username"
eval "$(ssh-agent -s)"
ssh-add c:/Users/YOU/.ssh/id_ed25519

now make a config file in ~/.ssh/ folder

# content of config file
Host github.com
  HostName github.com
  User git
  IdentityFile ~/.ssh/id_ed25519

ssh -T git@github.com