You will need a Hedera testnet account or preview testnet account to interact with and pay for any of the network services (cryptocurrency, consensus, tokens, files, and smart contracts). Your Hedera testnet account is what holds a balance of hbar to be used for transfers to other accounts or payments for network services.
To create your Hedera Portal profile register here and complete your profile.
Once you've completed setting up your profile, select the test network from the network drop-down menu and create an account. You can easily copy your accountId, public key, and private key information to your clipboard to use when configuring your SDK environment for testnet. The "NETWORK" section contains the node ID and node address of testnet nodes that can be configured in your application to submit transactions
You're now ready to build your application on testnet!