ProChannel Modularity allows you to insert new ProChannel modules by right-clicking in ProChannel's empty space and selecting Insert Module.
 

If you have installed a new ProChannel module and do not see it listed, it may be because SONAR needs to re-scan your installed VST plug-ins. If you have disabled "Scan For VST Plug-ins On Startup", SONAR will not have scanned automatically and you must manually re-scan.

To force SONAR to re-scan your installed VST-Plug-ins go to Edit > Preferences > File - VST Settings and then click on the Scan VST Folders button. After the scan is complete, your new ProChannel Modules should appear.