getting my ged at 17 (almost 18)

hey guys, I’m a 17 year-old kid from Gaithersburg Maryland and I’ve had a really tough high school experience and I won’t be able to graduate on time this year and I’m looking to get my GED. But I’m kind of lost and need help and I don’t know where to start. How long did it take to finish it? Did you guys take a GED program or did you study on your own? Any information helps please.