On the Jamorigins instructions for Sonar, I got to here and bogged down.
5.Launch Sonar. Add new audio track. Insert MIDI Guitar (now found in Soft Synths menu) to FX bin.(no problem, I called it "midi guitar" . I found the Midi FX and a midi guitar window pops up)
6.Go to Synth rack view. Right click grey area of the MIDI Guitar synth block and click “Enable MIDI Output”. ok done
That’s it. Add your favourite synth to a new track and route MIDI input from MIDI Guitar, (done) which should be visible in MIDI input menu
When i play, the meters in the "midi guitar" track respond but no sounds from the SI Strings instrument synth

Since we both have Sonar Plat......here's a very simple way to do it:
 
On an Audio track in the Fx bin, click the + sign and Insert Audio Fx > VST2 > Midi Guitar
then, open the Midi Guitar interface and click on Instrument (top right corner)......choose which synth you want to play and click on Edit (which opens up the Synth.....i.e. SI Strings and play your guitar)......simple :)) 

Hm, attached are the two interfaces of the midi guitar window. I don't see the word Instrument on the top corner.

I did see the instrument output on the first one.
Hitting manage instruments there, opens a blank window looking for instruments and vst's, but hitting scan tells me to do it as a stand alone. I couldn't seem to open a stand alone one.
 

I do not configure the MIDI Guitar plug-in as a synth. That was necessary prior to X3 but no longer. Also, I use a separate track for the synth. The setup goes like this:

• Add a mono audio track for guitar input
• Add the MIDI Guitar Plug-in to the FX rack
• Set "Enable MIDI Output" in the VST2 dropdown in the MIDI Guitar VST header
• Enable "Input Echo" on the audio track
• Add a synth either using a MIDI+Audio tracks or instrument track and load a program
• Set the MIDI or instrument track input to MIDI Guitar
• Enable "Input Echo" on the MIDI or instrument track

 
The pictures are a fairly old version of the MIDI Guitar and the ASIO buffer is a little high for good results.

Thanks Scook, I'll try this tomorrow.
Don't know why the pix would be old, I just downloaded it.
It is the free version however. Perhaps the paid one is different?

The paid version is not a beta although there is a v2 beta available. The first image is an old beta. The second image is the regular 1.0 release version. I purchased when the product was still in beta for v1 and have no experience with the trial package.

Thanks Scook it's working now.
Excellent instructions.
A bit of delay at this point, but maybe fixable with settings.
I had an old version as well as the new in the VST list, so I wiped them all clean and started over.
I'm excited.

The delay is the result of your audio buffer settings. The best results are had using an ASIO buffer setting of 128 samples or smaller.

experimenting