Windows 7 & Windows Server 2008 come with powershell installed by default
for all others you can download the installer here
Start > Run > Powershell
Set-ExecutionPolicy remotesigned
cd ([environment]::GetFolderPath([environment+SpecialFolder]::MyDocuments))
git clone git://github.com/truefit/WindowsPowerShell.git
exit
restart powershell
And run the following command to setup git configuration info and aliases
Setup-Git
Then run the following command to setup the truefit certificate and netrc file for auto login to the truefit repos
Setup-Truefit