I'm working on the "Quick Start: Salesforce DX" trailhead project, and in the section "Set Up the Project on Your Local Machine", I am getting the following error when trying to clone the app repo (step #2). 

I enter this into command prompt:
"C:\Users\Adam\my_sfdx_project>git clone https://github.com/forcedotcom/sfdx-dreamhouse.git"

This is what is returned:
'git' is not recognized as an internal or external command,
operable program or batch file.

I'm pretty new to command line and github, so not sure what to do. I do have Github installed on my machine.
Does anyone know how to resolve this?

Thanks in advance,
Adam