Installation is very simple. Just unpack the module and enable it. It requires Drupal 5 or later.
When editing a node a link appears beneath textarea's saying "Enable WYSIWYG". By default the textarea is the normal plain jane edit area, but if you click on this Enable widget then the widgEditor starts and changes the textarea into the pseudo-WYSIWYG editor.
It offers a skimpy set of features.. just Bold, Italic, a couple forms of Lists, and a thingy to incorporate images. While this is useful it's the bare minimum of what you'd want in a WYSIWYG editing experience.
Under the covers it creates halfway decent HTML. For example it uses <p> tags rather than <br> tags to delimit paragraphs.
By default Drupal uses the Line break converter and this throws a little wrench into the works. See Conflict between WYSIWYG and Line break converter