First step is to buy some bitcoin at for example coinbase. That link will give you 10$ of bitcoin for free with your first purchase of 100$.
Second step is to move them to bigger exchanges like Bitfinex or Kucoin where you can exchange them to other cryptocurrencies if you d like.
On Kucoin you can buy for example Kucoin shares which give you a passive income in dividend every day since the platform returns 50% of its fees to people who own Kucoin. Kucoin doesn’t require verification, just your own email address and a password and you’ve got an account! It’s the first to list Red pulse tokens and is one of the only exchanges that distribute GAS when keeping NEO on their platform. You can check out the other coins that they list here
Third step is to always do your own research in what to invest and buy low - sell high
If on the other hand you d just like to hold bitcoin for the long term and make sure they are secure, it’s best to buy a hardware wallet.