Well, how you learn a language depends on what language you're trying to learn. Some languages have more resources than others. Luckily Japanese has become very popular over the past few years because of anime and because Japan's economy is important on the global stage nowadays; thus there are a lot of ways you can learn it.

You might want to look at this similar thread for recommendations about that: https://www.italki.com/discussion/160360

Most of the resources I know of for advanced Japanese study are paid ones. If you Google "learn Japanese" you will find a lot of sites trying to sell you their services, but not many who are willing to help you for free. However one tip that I have for you is to search language learning blogs for resources, because many learners are resourceful in finding obscure websites. Here's a list of some of those: https://www.fluentu.com/blog/learn-language-blog/ , https://www.fluentu.com/blog/language-learning-blogs/ , https://www.lingualift.com/blog/best-language-learning-resources/

I don't know where you're at on your Japanese learning journey, but it's best to start by learning Hiragana and Katakana first, and learn their stroke order. This will ensure you can write properly and that you can start reading early on.

I recommend looking for news sites that offer their content in furigana or in simple terms so you can read more in the beginning stages. Here's an example: http://www3.nhk.or.jp/news/easy/

Good luck in learning!

Tanya made some good recommendations, I would also add the Japanese from Zero series.

If that sound too hard you try a Brain implant  

Hi, there are a number of options: search on the community here on italki for people who speak the language you want, and who are learning the languages you speak. You might be able to find someone who wants to exchange languages!

Also you can find teachers here for Japanese, if you want to spend a few dollars. Community tutors are informal, professional teachers can help with structured learning. It depends on what you might need.

There are also apps and sites: Amikumu is a great app for your mobile phone for finding speakers of a language locally, and also the website meetup dot com is good for finding local groups for your target language, to practice in person what you've learned through tutors and teachers or friends on italki.

Good luck!