Private keys are crucial in cryptocurrency, as they prove ownership and authenticate transactions. Ensuring secure management of sensitive values like private keys is vital, especially when using third-party APIs or service credentials that can sprawl out of control if not managed correctly. This tutorial will cover the basics of interacting with blockchain APIs from joining a peer upwards, focusing on the Ethereum blockchain, which is one of the most commonly used networks. The guide assumes no prior experience interacting with blockchain or web3 services and uses a testnet to limit potential exposure of sensitive information. It introduces Doppler, a secure and convenient way to manage secrets without risking unencrypted local file storage. The tutorial covers connecting to the Ethereum network, generating public keys, receiving tokens, sending tokens securely, and managing private keys securely using Doppler. By following this guide, developers can learn how to work with blockchain APIs in a secure manner, ensuring their projects are protected from malicious actors.