Do you have a proper idea for a story, a character and ideas and all that? If you haven't, then just reading loads and loads about your time period/subject matter really helps kick start inspiration. Other than that, just go for it! There's no real rules about writing any kind of fiction; it's kind of like the Code of the Brethren and all.
"TV makes sense. It has logic, structure, rules, and likeable leading men. In life, we have this. We have you." -Abed Nadir
Like Twit said, research that specific time period extensively. You want to know the ins and outs of the time period and events, etc. Writing historical fiction is like writing a story where the setting, era, and some of the characters and their actions have all been set out for you already. The rest of it is up to you! Any additional characters or little twists and details you add make it your own original work.
There are two kinds of folks who sit around thinking about how to kill people: psychopaths and mystery writers. I'm the kind that pays better. ~Rick Castle
Historical Fiction is all I ever write these days. I find it facinating and challenging. Read the tutorial I wrote about this genre here: post650572.html?hilit=historic#p650572
I'm also a historal Re-enactor of the American Revolution period going on my fourth year in the hobby. As such, I've grown adept at researching. So please ask specifically where you're stumped and I'll try and help.
My best advice is, you must learn patience and embrace it.
