The first step to buying Bitcoin is finding a reputable exchange. Some popular exchanges include Coinbase, Kraken, and Bitstamp. Once you create an account on an exchange, you will need to verify your identity. This usually involves providing a copy of your passport or driver's license. Once your identity is verified, you will be able to deposit money into your account using a variety of methods including bank transfer, credit card, or debit card.
Once you have deposited money into your account, you can start buying Bitcoin. Most exchanges offer a simple interface that allows you to buy Bitcoin with just a few clicks. You can also use more advanced features if you want more control over your purchase. For example, Kraken allows you to place an order on the order book or use margin trading.