Malaria Medicine?

I’m looking to travel to southern Africa in a couple of months and the WHO and state dept recommend malaria medicine. I haven’t been to my doctor yet (I don’t really have one) and I’m not sure how to get them or when I should start taking them or if its even necessary. I read there’s some crazy side effects. I’ll be there for about a month in South Africa, Botswana, and Malawi. Can I get buy with just bug repellent? DO they sell that there?

Also, any recommndations for safaris or tours or general tips and advice is much appreciated!