Try finding TUFS (Tokyo University of Foreign Studies) workbooks for beginners on the net if you're planning more regular approach of studying it. I have good memories of them, but it was years ago (the ones I have are ancient -- and all in Japanese lol -- published in the 1990s, there must be smth newer). Since then I wasn't practicing much of Japanese -- switched to Chinse -- so can't advise any better.
//Learning alphabet is like an hour, the rest is practice. Kanji might be a bit more complicated task -- there're plenty of separate kanji courses (how to write, memorize and search them), for basics even Chinese ones will do.