Well, you don't know a lot yet. But having an interest is the important thing. And it is interesting: as ( I think) Carlo Ginzburg said, the great thing about history is that it really happened. I'll make some suggestions- I am sure others will also.

Do the basics. And even the basics are interesting. Jill Lepore recently wrote an excellent history of the US, These Truths. It's got gaps ( if you want to learn about the actual fighting of the Revolutionary War, you'll have to get it from elsewhere) but it's good.

Good history should have footnotes and references. Take some time every so often and follow one up, see where the reference leads. You may go down a rabbit hole, but rabbit holes are part of the fun ( later, you can call it "research" and everyone will think you're working). And rabbit holes are much easier to go down, now, with digital libraries like JSTOR. Your school librarian should be able to help you with those.

Try to read some things you might dislike. For example, you'll find people who lean left and so only read Howard Zinn's A People's History of the United States, or lean right and only read Schweikart & Allen's reaction to Zinn, A Patriot's History of the United States. We all have some things we would like to be true- but if you only read what confirms them, you're not reading enough. There are also just bad books, and old obsolete books. Trying to read everything will drive you crazy, but don't reject reading something simply because it makes you uncomfortable. Being uncomfortable is part of the job.

Start learning a foreign language. It will open up a lot of sources for you in the future- not everything is translated into English. And High School is the perfect time to begin.

You are a work in progress. Do not be afraid to ask questions that might make you look foolish, or worry about getting everything absolutely perfect in a paper. Give it a try, don't sweat the small stuff..