Used the registration info in your Cakewalk account to install Addictive Drum from the XLN site
http://www.xlnaudio.com/en/install. This information should be in your Cakewalk store account in X3 download file 05_XLN_Audio_Addictive_Drums_Download_Instructions.rtf
Melodyne is part of the SONAR X3 install process. The installer will guide you through the registration process.
There is no need to download the DimPro files (or Loops and One Shots). They are the same as X2. If you do download and install DimPro, you will need to re-register the product.
Rapture is the same as X2 too. If you perform the basic install of X3 expect to re-register that product too.
TH2 Producer is the version that ships with X2/X3 Producer. If you purchased the full version of TH2, it was a download directly from Overloud and uses a separate installer. If it is installed and not showing up in the effects list verify the the path to the TH2 dll is in the VST scan path.
Also make sure to follow these
instructions after the upgrading to X3.