I don't seem to have the pitch correction tool showing in my tool box.  I tried pressing F2, but nothing happened.  Any help will be greatly appreciated.

Melodyne can be inserted as a track effect just like any other VST plug-in.  You can also access it by right clicking on a clip in the track view and selecting "Region Effect".
 
Please check out the documentation. https://www.cakewalk.com/Documentation?product=SONAR&language=3&help=Region_FX.01.html
 

If you are already in the Melodyne gui, make sure you are using the "melodic" algorithm, not "rhythmic (unpitched).

Good afternoon, I do not have all the tools I saw in the manuals. And I have it in "melody" algorithm. I can not find the one that is used to "flatten" the waves ...

Well,  when you go to the programs folder on your computer for Melodyne there is a tutorial that pop-up in the form of a video,  it presents you with all the first steps to using Melodyne. 
 
Also, if you go to the Celemony website and go to Help, you can access that same Tutorial video and select the essential version of Melodyne to see the features in which you have that comes with Sonar,
 
Click the link below,
 
Melodyne Video Tutorial

Thank you very much Jesse, I'm going to study this matter with patience. A greeting!

gabrielfran
Thank you very much Jesse, I'm going to study this matter with patience. A greeting!

No Problem and remember, the manual is installed on your computer and on the website as well.  Also, YouTube has a bunch of videos as well.  See the link below for YouTube Videos on Melodyne 4 Essentials
 
Melodyne 4 Essential

I just toured the manual and found no reference how to individually "flatten" the variations of a wave. You can control the pitch fluctuation to some extent, but that affects the track or the clip, not the note in question. In previous versions there was a specific tool for that, I remember seeing it.
Watching video tutorials takes much longer than reading a manual. Will I have to double my patience?
With the V-vowel it was very simple, I'm surprised that such a tool is so "hidden".
Thank you very much anyway.

.

You might not have certain tools available in the basic version that ships with Sonar.
Melodyne editor has more features to it.