Sorry, but pure HTML will not get you far. Zenphoto is a flexible tool and based on PHP. Theme are tied into that so you will need to get into PHP basics to learn how to do that.
Quote:s there some editor that I can install that lets me edit pages based on clicking on an area of the page and inserting an image and then clicking another point on the page and adding a link to a page? What I want is Frontpage for zenphoto or what we used to call wysiwyg.
Sorry, that is not possible. With Frontpage you create static pages using HTML. Zenphoto is a tool running on your server so there are no real static pages. There are generated on the server before you see them in the browser.
Themes are predefined with design and functionality and a suggestion so any changes you wish beyond that you need to do yourself.
They are however of course HTML files with PHP placeholders for Zenphoto's function calls. Look at the theme files for Garland and you will find div elements for the sidebars (leftsidebar). There you can insert your logo. For new pages you will have to insert a function that does this.
I strongly recommend to read the theming tutorial for the basics of Zenphoto theming.
I am sorry but there is no easier answer.