Cryptocurrencies can be easily purchased through various online platforms known as cryptocurrency exchanges. These exchanges allow you to buy, sell, and trade cryptocurrencies using fiat currencies (such as USD, EUR, etc.) or other digital currencies. Popular exchanges include Coinbase, Binance, Kraken, and Bitstamp. Before making a purchase, you'll need to set up an account, verify your identity (as required by the exchange), and possibly set up a digital wallet to store your cryptocurrencies, although many exchanges offer their own wallet services.