Downloading GitHub Desktop

Head over to this Site
Click on the button as shown here in this picture.

This will download GitHub Desktop for your operating system.

Installing GitHub Desktop

Open the installer, on Windows it will show like this -

After installing, Sign in to your GitHub Account. You can make one Here

Configuring Git inside GitHub Desktop

After Signing in, you will see the below screen.
Enter your Real Name or Username & your Email ID.