There are several ways to do what you want to do. Most historians that write books are in academia, which means they are university professors or doing post grad work. It is and can be satisfying, for me personally it was not as I need human interaction on a regular basis.

I use my degree in American History as a National Park Ranger. Every park has a Historian that ensures the information we present to visitors is as accurate as possible. At my park, I get to speak to the public, answer questions about the history and nature of the site. As new information is found or archives are opened or found we update the information.

Teaching is another route. Getting a degree in History then a teaching certificate (depends on location) will in most locations give you the ability to teach.

Docent, which work in museums, are subject matter experts and know and understand the history behind artifacts. Although you do not have to have a degree to be a docent it absolutely helps in conveying information and critical thinking.

As for writing, that was part of my degree in college. I had a capstone project that was 25-30 pages with full citations, primary and secondary sources to support my stance on the subject. Writing is not just something you sit down and do, you need to practice it, work at it, do it until it becomes second nature. I am not an expert but I feel that I could tackle more and more in-depth subjects with what I have learned.

Hello, that's a nice objective you have, educating people. I became a historian while I was studying in a public university. I already had a respectable amount of books read, but the number of works I read during University skyrocketed. As a historian you will spend most of your time reading, and a significant part of your activity will be talking and writing about historic events. Most historians become teachers, so you will have that opportunity to not only communicate what you have learned but to study even more. As a teacher you cannot stop reading and learning new interpretations of history.

If you feel like it, I recommend starting a blog or a YouTube channel about History. You'll be amazed with how many people are interested in History despite the bad image that some people has about it as a subject and of their teachers. There are also many platforms to share what you learn.

Very important, crucial, I might say, is that you not only focus on learning about the events (the History per se), but also read about how History is researched and how Historians reach their conclusions (Historiography, the study of History as a field of knowledge). That way you can go on and teach more people how to write History themselves!

Look at the thread I want to become a historian when I grow up. How do I achieve that?, with special thanks to /u/sunagainstgold and /u/commiespaceinvader.

/u/TenMinuteHistory also spoke on this topic during Episode 135 of the AskHistorians Podcast. The thread links to Episode 86, which will be of interest to you as well.