That’s right, it’s only visible under Appearance > Widgets, then you can drag it to your widget area on the right-hand side, presuming your theme supports widgets?
Once I drag the Enhanced Text Area widget into the widget area, and click to expand it, I get all of the fields I should have such as title, content, class etc etc. Saving works fine, and it displays correctly in my theme.
I am having an issue getting the button I generated to display. I tried it in the Twenty Twelve theme, but couldn’t get it to show up either. Does anyone know another work around? This is the only widget that I found that will let you embed CSS into your sidebar. I wish I could get it to work. HTML button generators are lame and I haven’t found any that have good samples.