Use your Gmail email address as your Root User Email Address.
Give your root account a name. This will pop up a lot, so I’d recommend something like your first initial and last name, so if your name is Jane Doe, you might use jdoe. If you think the company might grow, it will be better to use something like your company name or acronym and the word root or master. So if you own Jane’s Construction you might use “janesroot”
Follow the instructions to verify your email and set a password.
Set a secure password. Use LastPass if you like to generate a random password and remember that for you.
Turn on Multi-Factor Authentication (MFA). Like with your Google/Gmail account this adds a big amount of security to your account.