Before you install Git, it's a good idea to check to see if you already have it installed.
To check whether or not you have git installed, simply open a terminal window and type "git --version".
If you've already followed the video Installing Git for Windows on a Windows Machine you'll see a message like "git version 1.9.5.msysgit.0" . In this case you have Git for Windows installed, and can continue the series.
If you have not followed that video, and are using cmd.exe, you'll likely see a message like
'git' is not recognized as an internal or external command, operable program or batch file.
In this case, you don't have Git installed, and will benefit from installing Git for Windows as described in the video Installing Git for Windows on a Windows Machine on this site.