Put in an address and a link comes back. Open it and your key appears once. No account, no password, nothing to log into.
What the free key gives you: 50 calls a day, 30 an hour, every endpoint, no expiry. Enough to try the model against your own sequences and decide whether it is worth anything to you.
If you need more, use the form and say what you are working on. A person reads it, and the limit is raised to whatever your work actually needs.
By using a key you accept the terms: research use, not a diagnostic result, and do not share the key.