I wouldn't say that you need an app to learn the alphabet. I found it (my friends, too) quite easy, it's only 24 ''letters'' that you need to remember. Of course, proficiency will not come instantly, but correct pronunciation/differentiation will follow as you read and write. TTMIK is hands down, the best Korean learning website there is. The course is levelled, as each level has a book (not necessary, but I have purchased some along my journey) and each lesson has a PDF and audio file. The hosts are quite funny and cheeky too. They have an app and a huge community, that's how I got my head start. Korean takes a bit to crack down, but once you get there, it's easy. Good luck!