Working with the registry is fairly easy you have the PSProvider that let's you treat the registry just like a file system. However adding keys is a bit more tricky.
Set-Location HKLM:\SYSTEM\CurrentControlSet\Control\SecurityProviders\SCHANNEL\Protocols\SSL 2.0\Client
New-ItemProperty -Path . -Name DisabledByDefault -Value 1
However at this stage in the game rather then trying to automate by script you may want to take the oportunity to learn PowerShell Desired State Configuration it makes stuff like this easier to repeat and more industry standard.
-VERN