Go to the main site of Leonardo.Ai: https://leonardo.ai/
Click the Launch App button.
Or go directly to the web app site: https://app.leonardo.ai/
It offers logging in with an Apple/Google/Microsoft account, but it’s not recommended. Make a normal Leonardo.Ai account.
Below the Sign in button:
Next to „Need an account”: click the Sign up text.
Paste your email address and a password.