If you want to store bitcoins, then a wallet is where you keep them. Altcoins are traded globally on hundreds of exchanges. Lucky for you: It’s easy to find where to buy bitcoins online because there are so many options. Online wallets are vulnerable to hackers, so carefully research a company’s security features before trusting them with your bitcoins. Is the exchange trustworthy? Most exchanges that let you buy bitcoins also let you sell for a fee of course.