How to set up 32bit vst instruments in sonar 8.5 64bit

It is not included with Sonar.  It is a separate product you purchase that works with Sonar.  He frequently updates it as well to get as broad a function set for 32bit VSTi's to function in 64bit. Think its around $30.00
or 15.00Eur
Excellent product and support.

http://jstuff.wordpress.com/jbridge/

Sonar automatically uses its own Bitbridge to run 32 bit vst's in a 64 bit environment. If this isnt working for some of your plugins then you might want to purchase JBridge.

Sonar is already set up to use JBridge but you have to pay and install it separately. Once installed, open up Cakewalk PLugin Manager under the tools menu.  Scroll through to find the plugins you want to run under JBridge. Pro 53 and FM7 will be under Vst Instruments. Select the vsti and select Plugin properties and select Jbridge. Its that easy.

I have both the 53 and FM7 working with JBridge.

As has been mentioned, the OP's problem is almost surely how his VST plugins folders have been organized/setup.
 
To keep things manageable, I'd suggest using two separate VST Plugins folders.
 
64Bit Plugins:
Create a VST Plugins folder under C:\Program Files\
 
32Bit Plugins:
Create a VST Plugins folder under C:\Program Files (x86)\
 
Always make sure to install to the correct plugin folder (32Bit or 64Bit), otherwise you'll be mixing the 32Bit and 64Bit plugin dll files... and you'll have a mess. 
By keeping the 32Bit and 64Bit dlls separated, you maintain separate control over each group.
 
Once you have the Plugins installed in the above manner, setup Sonar to scan both plugin directories.
 
Sonar will automatically use BitBridge for 32Bit plugins.  (Requires no input from you)
Note that most plugins now work fine with BitBridge... but some don't.  For those that don't, JBridge (3rd party applet that bridges plugins) usually works.  JBridge is ~$21
 
Also note that you can install both the 32Bit and 64Bit versions of Sonar under Windows x64.
If you have a 32Bit (code) plugin that just won't cope with being bridged, you can always fire up the 32Bit version of Sonar and get your work done.  Freeze/bounce that particular plugin... and then you can open the project (again) in the 64Bit version of Sonar... and continue/finish. 

The brute force method is to load them in a project. If opening the GUI for the plug-in creates a separate program icon on the Windows Taskbar that looks like a little blue adapter plug, that's Bitbridge (a.k.a. Teleport Server) hosting a 32-bit Plug-in.