Again the right thing is different for everyone. nearly everyone has already experience with learning a second language in school so you could use that as a guide to plan learning japanese now. Or in case you are one of the few people that don’t you can learn about ways to learn a language, creating milestones and goals etc. first before you start learning. There are countless polyglot Youtubers that describe their journeys and the things they think are important or guides on the internet that can help you learn how to learn a language.
There are many resource lists for learning japanese at different stages in this forum. There are also guides on how to learn japanese (like this: “Minimal Guide to Learning Japanese”), journey descriptions, study logs and hundreds of people that made a threat to ask how they should learn japanese or ask for ways to improve their learning methods (like: Requesting ways of improving my learning journey) that have helpful comments.
If you have as much free time as you say it would be easy to look at the things that are already there.
Or if you want something that really fits you without putting a lot of work in you can make a thread and really describe where you are and where you want to be in a certain point of time and ask other people for help. Because people can’t help you if you don’t give them information. How long do you plan to learn japanese? Is your focus speaking/listening or reading. Do you want to learn to write Japanese properly? Do you want to take the JLPT. DO you learn because of work reasons?
All these things have to be taken into consideration if you want to get a good answer that is actually helpful. Someone who learn for work reasons will have a complete different focus than someone who wants to pass the N5 test or someone that just wants to learn how to read manga. So the answers would all be very differently.
But if you barely say anything except for I have a lot of time it is nearly impossible to really help you. You’ll get the same generic answer that all the other hundreds of people that make threads like this get too. Depending on how much the generic answer fits you it might be helpful or not at all. But that is also something you’d get with a five minute research in this forum or on the internet.