If you’d like to add a new course to your list, scroll down in the course list; note that you can only add original Memrise courses; for community courses, you’ll have to add these on the web (i. e. start a learning session on the web, after that the course will sync to the Android app)
If you have a sub and are thus able to actually download courses for offline use, select your course, then tap the Learn button at the button; the download-button will appear near the top right
ah, here it is, thanks for the pointer. Given that most of my courses are done ‘learning’ and only get revised (which you can do from the main page) ‘learn’ was not a button that looked like it needed clicking!
Slightly strange to have a second page, doing mostly the same things in a slightly different manner?