Bitcoin is treated like a commodity in most places. Businesses like Coinbase, Kraken, River, and Binance are easy places to get started.
Cryptocurrency exchanges like these require you to set up an account, much like a bank. After setting up an account, you can wire funds to the exchange or use a network like ACH or SEPA to transfer funds to your new account. Then, buying bitcoin is as simple as placing a buy order.
One of the reasons so many people are interested in Bitcoin is that it is money that doesn't require a third party. After you buy Bitcoin at an exchange, it is a lot like having money in a bank. Until you withdraw your Bitcoin, you are trusting the exchange to remain in solvent.
Like cash, you can withdraw your Bitcoin from your account on an exchange. This is often called taking custody of your Bitcoin or "holding your own keys." With a few precautions and a little education, it is a straight-forward process and allows to be in control of your money.