The first thing you need to do is verify where your plug-ins have been installed.
If Sonar is in 64 bit mode, your plug-ins should be installed here:
If Sonar is in 32 bit mode, your plug-ins should be installed here:
If your plug-ins are not in the correct folder, then re-install them into the correct folder or make note of the folder where they are actually installed.
Once you have verified the plug-ins location, open Sonar...
Go to Options > Global Options.
The plug-in folder that you installed to above should be listed in the VST Scanned Folders window. If they are not, click "ADD" to add that folder to the list.
Make sure the Scan for VST Plug-ins on Startup is checked.
Click Scan VST Folder down at the bottom.