You'll need Polkadot Extension in your browser to create a new wallet account. If haven't installed it yet, you can follow these instructions on how to install the Polkadot extension.
Follow the instructions to generate your new key pair.
Please keep your private key secret. During the preview stage, tokens in this account are not real TEA tokens and can only be used on the testnet. But it's still good practice to keep your private key as secure as possible.