Create a Github account at https://github.com
Go to https://destkop.github.com and download the appropriate version of GitHub Desktop for your operating system.
Click on the installer to begin installation. Once, the installation is finished, sign in to your Github account.
You may or may not have Git installed. To check for that, open a Command Prompt or a Terminal and type in git --version .
If it does not output a version and does not know what you are typing, you may want to download git following these steps: https://git-scm.com/book/en/v2/Getting-Started-Installing-Git