You need three major things:
1) Tools to extract the text and pictures from the game in question.
2) The actual files in a format that can be read and edited.
3) A complete understanding of the Japanese language.
There are no shortcuts to translating. Either you know the language or you don't. Either you have the ROM hacking skills necessary or you don't. You can't just run the text through something like Google Translate or Bing Translate because neither will return results that actually make sense half the time, and the rest will be incorrectly pieced together or just generally mistranslated.
Now, if you have any skills to bring to the table past "I want this game translated", and especially if you can get some work done even on the ROM hacking side of things, you're always free to try starting up your own project and seeing if you can attract anybody who speaks Japanese who would be willing to help you. I strongly suggest against making a topic saying you simply want a game translated though while having nothing to offer. It will be locked, and nobody wants to jump on a project simply because you want it done. The translator generally will want to have some interest in the title(s) in question as well, so even if you know how to do part, if no translator is interested in the project, you're just out of luck.
If you would like to start learning Japanese, I recommend starting off this Densetsu's Japanese beginner tutorial. It's well put together with other members contributing other great online, free resources to start and advance through learning the Japanese language. I'll link the tutorial in question below so you can have a look:
https://gbatemp.net/threads/learning-japanese-the-nihongo-faq.290986/
Otherwise on the ROM hacking side of things, when I say tools need to be made, I mean programs need to be built basically for every individual game as they tend to all be put together differently. Extracting varies as well as reinsertion based on game limitations, but generally once you can actually get into the files, some more common editing tools can be utilized. All in all, both learning the language and the ROM hacking would be years of practice until you were truly ready to dig into a translation solo, so maybe you should focus on learning one aspect. If you decide on Japanese itself, it will save a lot of work and will save you from depending heavily on others for your own desires.
