$nic=Get-Netadapter
$password = "some_secret_pass" | ConvertTo-SecureString -asPlainText -Force
$username = "some_AD_domain\some_user_id"
$credential = New-Object System.Management.Automation.PSCredential($username,$password)
$currenthost = $env:COMPUTERNAME
Set-DNSClientServerAddress -InterfaceIndex $nic.ifindex -ServerAddresses "x.x.x.x","y.y.y.y"
Add-Computer -DomainName some.domain -Credential $credential -ComputerName $currenthost -NewName NewTest -Restart