Here are the steps to follow:

• In the Jenkins dashboard, navigate to the desired Jenkins job and click "Configure".
• Scroll down to the "Pipeline" section and select "Pipeline script from SCM" in the "Definition" dropdown.
• Choose "Git" as the SCM, and enter your GitHub repository URL https://github.com/devopsrange/jenkins .
• Leave the "Credentials" field empty.
• Set the "Script Path" to the path of the Jenkinsfile in your GitHub repository (e.g., Jenkinsfile).
• Click "Save" to save your pipeline configuration.
• Once saved, Jenkins will automatically fetch the Jenkinsfile script from your public GitHub repository and execute it whenever the Jenkins job is triggered.