Activate Claim Based Authentication afterwards with PowerShell

You can active Claim Based Authentication for a SharePoint Web App afterwards if you missed that at creation time.

Use this PowerShell script:

Add-PSSnapin Microsoft.SharePoint.PowerShell -ErrorAction SilentlyContinue
[System.Reflection.Assembly]::LoadFile($Env:CommonProgramFiles+"Microsoft SharedWeb Server Extensions14ISAPIMicrosoft.SharePoint.dll") | out-null

$webapp = Get-SPWebApplication "http://<sharepoint server>/"
write-host "Current: " $webapp.UseClaimsAuthentication
$webapp.UseClaimsAuthentication = $true
$webapp.Update()

$webapp.ProvisionGlobally()

write-host "    New: " $webapp.UseClaimsAuthentication