If you want to invest bitcoin, you must understand it, first a safe wallet. I recommend using cold wallet like: Ledger nano S, Trezor, or if you don't have the money to buy wallet types above, blockchain.info is also a very safe option. A secure wallet is the most important thing in investing in bitcoin, or any other type of altcoin, you won't want a hacker to visit and take your entire bitcoin someday.
Next you have to learn about Bitcoin trading, a safe trading place, I recommend buying on reputable exchanges such as Coinbase, Remitano.. These are platforms that allow you to buy Bitcoin and some altcoin with fiat money. So it is very convenient for a small investment.
And it's important to believe in the future of bitcoin, invest in it with a long-term intention. If you think you can get rich quickly with bitcoin, you should stay away from it, bitcoin has potential, but no one knows what will happen in the future.