You sign in with your email address and a six-digit code we email you. There is no password, and no separate sign-up: the first time you sign in makes your account.
You don't need an account to start. Build the whole invite on New event first: the name, the date, the place, the people, the photo and the look. When you get to Send, the button reads Sign in, and nothing reaches a guest until you have.
The invite you built waits in that browser while you sign in. The sign-in page shows its name, when, where and how many people, and afterwards you land back on it, ready to send.
Type your email and press Continue, then type the code from the email and press Verify. If the code doesn't come, check your spam folder, or press Send it again. A code only works for a short while; a fresh one always does.
The first time, we ask for your name, because every invite goes out under it, and offer to save My place, where you usually host. You can change both later in Settings.
To sign in with a different address, open Settings, then Change beside Email. We send a code to the new address to confirm it's yours.