Can't say much about WYSIWYG but, while such editors are much faster to get something up and running (not as fast as using a CMS like WordPress), to actually learn something I would strongly suggest starting with w3schools.com and Notepad++.
Nothing beats understanding the code behind your page.
Please don't recommend w3schools . I would recommend the Mozilla Developer Network.
About CMSs, I would recommend Joomla, or Wordpress. I think you went to the wordpress.com site, which is a blogging platform that is built on Wordpress.
Learning can be done from experimentation, but that takes some time. You can use something like Codecademy or Code School to jumpstart your learning.
Personally, I learned HTML, JS, and CSS from fooling around with Bootstrap (by Twitter). I really like Netbeans for HTML editing.
But you want a WYSIWYG HTML editor, I would recommend BlueGriffon, a fork of Kompozer. I recommend BlueGriffon over KompoZer because it has been updated later than KompoZer.