Using a web browser · Sign in to Coinbase. · Select Buy / Sell on the upper right-hand side. · Click the Buy field to select the asset you'd like to purchase. · Enter the. Coinbase is the most popular platform to buy cryptocurrencies like Bitcoin, Ethereum, and Litecoin. May not have as many altcoins as some other exchanges. Start with our list of top cryptocurrency exchanges for altcoins. Some exchanges let you trade altcoin-bitcoin pairs, meaning you can buy and sell altcoins Coinbase offers about 40 different altcoins to choose from and it.