If you haven't downloaded the software yet, you can download it here: http://www.acoustica.com/pianissimo/download.htm
To complete the registration process, please run the stand-alone Pianissimo and click the "Help" menu, followed by "Enter Registration Code". (You may also click the "ying-yang" symbol on the top left of the screen to bring up the register dialog.)
Type in or copy and paste your "Registration ID" in the Step 3 edit box and type in or copy and paste the 20 character "Registration Code" (excluding dashes) into the Step 4 edit box.
Click the "Register" button and you're registered!