Your route to publication very much depends on what you're writing about, how significant your claim is and how ambitious you are. Depending on your research, the most straightforward option may well be through a local history society - many run their own journals containing research done locally or about local subjects, though how they define 'local' might differ, and might or might not include what you're doing.

Beyond that, there are any number of online publications, covering a vast range of topics, and with a broad spectrum of editorial policy. Some might care only that your piece is interesting and well-written, others might have stricter requirements for submissions. Without knowing more about what you're writing about, it's impossible to make specific recommendations here. A good rule of thumb might be considering where you've read papers that you yourself have valued/enjoyed, and checking what their submissions policies are.

Lastly, you can try to submit it to a scholarly journal in a relevant field. Again, standards and focus vary, but broadly speaking you would be expected to submit your paper for peer review - that is, anonymous evaluation from experts in your field, who will judge how far your claims and methods stand up to detailed scrutiny. This, even for professional scholars, can be a painful process. Crucially, it requires an ability not to just present evidence, but to contextualise it, showing that you're aware of scholarly work that has been done in your area, and how your argument advances our collective knowledge in your field. Depending on the journal, they will likely apply some kind of significance test - that is, why does it matter that you've done this this research? Why should they, and by extension their readers, care? There is, perhaps less officially, an expectation that you will present your work in certain ways - both in terms of how the paper is structured, as well as how it presents and records evidence. Learning to do this is a big part of doing a degree in history - university-level history essays are designed to approximate the skills and approach that historians take towards writing research papers for publication. I obviously have no idea what your own background and experience is here, but its worth noting that they will expect you to conform to their standards rather than the other way around, no matter the value of your findings. Overall, this is a difficult process, particularly for an independent researcher - some editors will far more readily reject out of hand a submission from someone who isn't affiliated with a university or similar institution.