Option 1: Install posh-git via PowerShellGet on Windows (Best Way)
posh-git is available on the PowerShell Gallery and can be installed using the PowerShellGet module. To get it done through this route, Start either Windows PowerShell 5.x or PowerShell Core 6.x (pwsh) as an administrator, install PowerShellGet

Install-Module PowershellGet -Force
Then execute one of the following two commands:

For a completely new installation

##A completely new installation
PowerShellGet\Install-Module posh-git -Scope CurrentUser -Force
For a updating posh-git if it has ever been installed from PowerShell Gallery

PowerShellGet\Update-Module posh-git