To do this, you will require the User Admin and Groups Admin role in Google Admin and Security Roles.
Click 'Add User'
User emails must always be formatted like this and always use the Neuromatch.io domain.
Put their personal email in the 'secondary email field', and then click save. In the popup, click the button to send sign instructions, and it will automatically send signin instructions to their personal email.
Finally, add the user to the 'Everyone' group as well as any specific groups for their team or role type.