>>24564
I'd recommend getting some Japanese language textbooks and going through them. If you're a native English speaker, I'd recommend the Genki series of books, since that's what I used. http://genki.japantimes.co.jp/index_en
Otherwise, it might be best to find textbooks for your native language. It's very important to learn the basics of the language, and language textbooks are good for that. At a bare minimum, you need to know:
1) all the kana
2) the basic particles: は、が、を、の、に、へ、から、より、と etc
3) verb forms: ichidan and godan forms for present, past, negatives, te-forms, causative, passive, potential, and combinations thereof. Basically everything on this chart https://upload.wikimedia.org/wikipedia/commons/6/68/AMB_Japanese_Verbs.pdf
4) adjectives: i-adjectives and na-adjectives
5) quotation and discourse
6) attributive verbs and sentence order
7) some kanji. Because of handwriting recognition, multi-radical search, and OCR, it's not super critical to learn to recognize all the kanji on sight. But the more you know, the better.
Once you've mastered the fundamentals, you can improve your knowledge by practicing translating. I learned a lot by writing out translations for manga. At first I encountered a lot of grammatical forms I wasn't familiar with, so I had to check my Japanese-English grammar dictionary very frequently (note: find an actual dictionary of grammatical forms, don't just use a general-purpose dictionary for grammar). I think the most important thing at this stage is to force yourself to learn from your mistakes. Recognize when you don't know something, and put in the effort to find an answer. Never let yourself be satisfied with a guess, because then you'll just get in the habit of guessing. Since manga is a visual medium, it's often really easy to guess what the text means. That's not the same as translating, and if you rely on that too much then you'll end up making a lot of mistakes. I think we've all seen manga where the "translator" very obviously just recognized a few words in each line and extrapolated from there without actually understanding what was being said.
Anyways, I think there are enough resources available that anyone who solidly knows the basics of Japanese can put out a decent translation with enough time and effort, and you'll learn more through the process.