The r/AskHistorians FAQ wiki is always a good place to start! Almost as good as Wikipedia (I joke, please don't kill me).

As you say, huge and open-ended. Maybe one place to start is to realize just that. Many of us who are trained as historians of Africa end up resenting a major dimension of that training, which is that we're expected to speak to and often teach to the entire history of a continent bigger than Europe or North America from the beginning of time to yesterday.

I don't say this to criticize the OP. Think of it this way: if someone said, "Where do I start with the history of Europe, including Scandinavia, Asia Minor, and Western Russia as well as Eastern and Western Europe and the British Isles, from the earliest human settlements to today", I don't think that questioner would feel uncomfortable if the response was "well, hang on, do you mean classical history like the Roman Empire? Medieval Western Europe? etc."

So the right starting place is to pick a place and time: when you say "I don't know African history", what's first thing that comes to mind that you don't know? Anything, any word, any place, makes the question vastly easier to answer.