[System.Reflection.Assembly]::LoadFrom("C:\Program Files\Windows Server\Bin\Wssg.Web.DomainManagerObjectModel.dll")
$CertMgr = New-Object Microsoft.WindowsServerSolutions.RemoteAccess.Domains.DomainCertificateManager
$certfile = Read-Host "Enter path to certificate PFX file"
$password = Read-Host "Enter Password to PFX file" -AsSecureString
$CertMgr.ConfigureCertificateFromFile($certfile, $password)
Please also review this blog post - http://blogs.technet.com/b/sbs/archive/2011/08/04/how-to-install-your-existing-certificate-into-sbs-essentials.aspx
What if my domain name is provided by GoDaddy as well as my cert (Domain name set at GoDaddy before running wizard)?
Yves ask in the www.sbsessentialsforum.com not here.
See Robert Pearman's script here:
TechNet SBS 2011 Essentials Manual SSL Installation Script:
gallery.technet.microsoft.com/SBS-2011-Essentials-Manual-5ad9ce1e