Install the necessary plugins for the repository (ex: GitHub install GitHub and GitHub Authentication plugins) in Jenkins.
You can generate a key with Putty key generator, or by running the following command in git bash: $ ssh-keygen -t rsa -b 4096 -C your_email@example.com
Private key must be OpenSSH. You can convert your private key to OpenSSH in putty key generator
SSH keys come in pairs, public and private. Public keys are inserted in the repository to be cloned. Private keys are saved as credentials in Jenkins
You need to copy the SSH URL not the HTTPS to work with ssh keys.