Assuming you have a Business Account, there's a feature that supports what you want to do. See this link to get started. Note, you will be assigning a User ID and Password to that person. The User ID is not an email address, it's a name you make up and you also make up the Password. Neither can be changed by the user - only you. Next, you assign the person their access privileges. In order to test everything, you can log out of your account, then log back in using the User ID and Password - that way you can see how this setup works and then show the user how to login.
