1. Find and register with an exchange that supports the altcoins you want to buy.
2. Verify your account. Depending on the exchange, this might require uploading government-issued IDs.
3. Transfer funds into your account. You can usually do this with a credit or debit card, or through a bank transfer.
4. Buy the altcoin you want. You can sometimes do this directly from your account.
5. Withdraw your digital coins to an external wallet. This is an important security step.