I have all my tracks recorded. So...how do I create the stereo mixdown track, and where is it stored? (The one that I would get after going through the mixing process and eventually export.) Basic, I know, but I don't see it.
Thanks, Larry

First click a track, any track, to be certain you aren't focused on a bus.
Next go: Edit, Select all.
Next go: File Export. The dialog box will take you from there.
 

But where is the mixed down stereo track, with all my fader movements etc.? I don't want to export the individual tracks, I want to export the mix. And I think I can make several different mixes and save them all, and pick the one that's best. Right? Where are they?

As Bitman mentioned, go to File/Export. there is a dialog box choose (What you hear) Stereo mix.
Take note of where your file is being saved. <- That one is a no brainer really. your save location is where ever you choose.

By default SONAR exports to the path specified in Preferences > File > Folder Locations "Wave Files"
Here is the help file for the Export Dialog.
Tutorial 9 includes a section on the export process and more from the help pages about the export process.

Great advice from Scook.

You'll get it. Just takes a little practice doing first few projects through the deliverable.

And my advice is to use "select none" there are many cases where "select all" misses certain parts, don't know why and it's only sometimes, but select none Ctrl/Shift/A   has worked for me for 10 years of exporting songs. 
And I never have to change anything in the export dialog box I've always used what ever the default is. 
Only change I make is the bit rate to 16 for CD burning. 
 
And as said you set the folder path in preferences. Mine is set to the root of my Sonar data drive "E"  From there I browse to the  "album" folder I want to save the Wav file to. 
 
When you have your mix sounding the way you want it:
 
check your master buss is not going over etc. (I like the BT Brickwall set at   -.4 ) 
 
File/ Save   - do this so your guaranteed all changes are in the export. 
Ctrl/Shift/A - to select none.  
File/ Export / Audio
I use the default setting and at this point will change the bit rate if required. 
Browse to the Album folder 
Type the songs name
Save and wait the 10- 30 seconds for the rendering. 
 
 

Thank you all. With this help I should get it.
Larry

lp.musman
 And I think I can make several different mixes and save them all, and pick the one that's best. Right? Where are they?

Not sure if you are talking about the resultant (usually) stereo result as has been described by everyone, or if you want to save different mix setups. (Could be you're coming from a DAW that has such a feature?)
 
I think the only way to do this is to save the entire project first (MyProject_mixA), then save again under another name (MyProject_mixB) and do a different mix setup there. Continue until you have as many as you like. You may like to restart with the original project each time.
 
You can open several projects at the same time in Sonar. Just position them so it's easy to select them. Stop and start each one to compare them.