Compatible with Version 3.6.
Copy the contents of the httpdocs directory to your root Ubercart folder
Navigate to Administrator > Modules. Scroll down the list until you reach 'Ubercart - Payment'. Select Cardstream from the list and click Save Configuration at the bottom.
Navigate to Administrator > Store > Configuration > Payment Methods. Check Cardstream from the list and click edit to enter your Merchant ID, Signature, etc. Click Save Configuration.