If you've memorized hiragana and katakana that is a good start. Studying kanji by itself will do little good if you don't understand the sentence the kanji is in. That being said kanji is also very important. Best thing to do is to take is slow. There is a lot to learn and it's not going to happen over night. Start with simple grammar. "I am Sam." "It this your pen?" that sort of thing, at the same time learn the kanji that come up in these sentences. Often you can find lists of kanji online started with the most used logographics. For example 私（わたし） is often one the first characters taught in Japanese classes because it is very common also not very difficult. Good luck in your learning, and just remember that the best way to learn a language is to use it. So practice practice practice.