1) Sign up or login to the app here.
2) Click the ‘Sign in with Google’ button on the right:
3) Sign in to your Google account
4) Click the checkbox next to ‘send email on your behalf’ on the screen that looks like this:
(We do not have access to read any of your e-mails, and we only send e-mails to your contacts when you explicitly ask us to)
5) You’re all set!