SONAR supports both VST and Direct-X plug-ins.  You will first need to determine which of these two types of plug-ins you have.  Most third-party plug-ins are VST. 

For VST Plug-ins:

When installing your new VST, be mindful of the directory where it is installed.  Common default locations include:

• C:\Program Files\Cakewalk\VstPlugins   (recommended location)
• C:\Program Files\Steinberg\VstPlugins
• C:\Program Files\VstPlugins

VSTs appear in SONAR via its integrated VST scanner.  If you’ve installed your VST to a common location like the ones above, you may not need to take any additional steps.  If the new plug still does not appear however, you will need to point SONAR’s VST scanner to the exact directory where your new VST is installed. 
To do so:

1. Click Options | Global | VST Plug-ins.  In versions prior to SONAR 6, use the VST adapter which is usually found from Start | All Programs | Cakewalk.
2. Click the Add button and browse to the folder where the new plug-in is installed.  Specifically, VST scanner looks for dll files.  So for example, the file PerfectSpace.dll is found under C:\Program Files\Cakewalk\VstPlugins.  You will probably notice that this directory has already been added by default and thus Perfect Space appears automatically.  Once you have located the folder containing your new plug-in’s dll file, click OK. 
3. Now click Scan VST Folders.  Click OK to exit Global Options.  Your new VST should now appear in your plug-in menus. 

For Direct-X Plug-ins:  

Usually, no additional setup is needed for Direct-X plug-ins.  Direct-X plug-ins install globally into Windows and are seen by any program that hosts them.  If your new Direct-X plug-in is not appearing in SONAR, first check to make sure it is installed properly.  If you are confident it is properly installed, then the plug-in may be excluded from your plug-in lists.  To check:

1. Click Tools | SONAR Plug-in Manager.
2. Click “Excluded” or “Show excluded” in the lower left. 
3. Highlight the type of plug in the “Plug-in Categories” list on the left.  If your plug-in is excluded, you should see it in the right column.  Highlight it and click “Enable Plug-in.”

Please click here for another VST related issue specific to SONAR Home Studio 7 and Guitar Tracks Pro 4.