The first step in learning Japanese, is learning the kana, or the two Japanese syllabaries.

I don’t recommend isolated grammar study, or the beginning of grammar study until you have a good chunk of vocabulary (500-2000 words).

After learning kana, for vocabulary, I advocate the use of a software called Anki. For a comprehensive guide on using this software I recommend this video, and to start with this flash card deck.

For a more comprehensive guide, look here.