I can't find 'empty trash'.

Right-click Trash in the folder pane.

Thanks for that specific answer, but I was really looking for an overview of the basics -- such as 'empty trash' -- in Thunderbird. Help contents 1 sends me to complicate questions and answers that aren't what I am looking for, and are way beyond me.

This may help. http://en.flossmanuals.net/thunderbird/

You have to go searching through the manual, page by page, to finally find the simple information you need. Is there some other way to access 'how-tos'?

You can Google your questions and usually find an article or ask them here. This is a volunteer operation. You could step up and write some instructions to your liking.