Adding New Theme to Defaults

I’m new to WordPress and just trying to add a New Theme from ww.wp.xz.cn through my WordPress SiteAdmin app.

In the Docs, it says there should be an “Add New Theme” option under the Appearance/Themes menu…but I don’t see it anywhere. It just displays my Current Theme and a selection of Available Themes (but the one I want is not currently listed in my Available Themes.

I know I could possibly manually upload through my FTP site, but my I’m having difficulty doing that as well and thought I’d try the easier option first.

Thanks for any assistance you can provide.