I think there are special portals about cryptocurrency trading and there you can find articles with detailed explanations for beginners, for example, this article https://hiribi.com/blog/how-to-buy-and-sell-bitcoin-in-kenya/ can help you find official websites where you can buy, store or sell cryptocurrency. I know that this is a rather detailed article and you can learn more about cryptocurrencies and how to invest in it correctly. It seems to me that it's important that you use only sites with a good reputation that can really be safe for such transactions.