When doing research into a topic you don't know a lot about, start by looking up reliable background material to give yourself a sense of what's going on. For this class, look up your specific countries in the following encyclopedia. The African History Encyclopedia will have shorter, easy to read entries. The Oxford Research Encyclopedia of African History will have more in-depth discussions with recommended reading at the end. Don't cite to either - they're to get an overview and don't count as solid scholarship.
After getting an overview of your specific countries, take a look at the Oxford Handbooks. These are actually scholarship with more reading suggestions.