There are several ways to buy Ethereum (ETH), including:

1. Cryptocurrency exchanges: The most common way to buy ETH is through a cryptocurrency exchange. Some popular exchanges that support ETH trading include Binance, Coinbase, and Kraken. To buy ETH on an exchange, you will need to create an account, verify your identity, and then deposit funds using a bank transfer or credit/debit card. Once your funds have been credited to your account, you can buy ETH at the current market price or place a limit order.
2. Peer-to-peer marketplaces: Another way to buy ETH is through a peer-to-peer marketplace like LocalEthereum or Paxful. These platforms connect buyers and sellers directly, and you can buy ETH using a variety of payment methods, including cash, bank transfer, and PayPal.
3. Bitcoin ATMs: Some Bitcoin ATMs also allow you to buy ETH using cash. To do this, you will need to find a Bitcoin ATM that supports ETH purchases, and then follow the instructions on the machine to complete the transaction.
4. Over-the-counter (OTC) trading: Some OTC trading desks specialize in buying and selling large amounts of cryptocurrency, including ETH. They can offer a more personalized service and better prices than exchanges, but they may require a higher minimum investment.

Regardless of the way you choose, it is important to do your own research and consider the fees, security, and reputation of the platform before buying Ethereum.