After you've request an ambassador address, you can integrate your ambassador mail address to Gmail, and this tutorial will step-by-step to lead you add your ambassador mail in Gmail's setting.
Step 0. Open 2FA (2 Factor Authentication) in Google.
Step 1. Open Gmail setting, switch to "Account and Import" tab, in "Send mail as" section, click "Add another email address".
Step 2. In add email window, enter your name and ambassador address, check "Treat as an alias".
Step 3. Fill SMTP information, use smtp.gmail.com as SMTP server here, and fill in your Gmail account in username field and 2FA password in password field.
Step 4. Check your mailbox, and find confirmation code in Gmail confirmation mail.
Step 5. Congratulation, You are ready to send mail by this mail address now.
Step 0. Add Google Apps one-time password
Enter Google Account Console, generate an one-time password with "mail" app and "Mac" device, device option doesn't matter, just a description for this password.
Step 1. Open mail client preference, I will use "AirMail" for example here.
SMTP server: smtp.gmail.com:465