First, make sure that you have Git Bash installed on your machine and that you select ‘Use Git and optional Unix tools…’ when given the option.
Open the Git Bash command tool and run:
$ ssh-keygen -t rsa
When asked to enter a file name, leave it blank to accept the defaults.
Enter a password if you like.
Once it is done, you can find your new ssh key in : C:\users\[your user]\.ssh
You can copy it to your clipboard with (assuming your in C:\users\[your user]\.ssh folder):
$clip < id_rsa.pub