Adding a Google Manager or Owner to Your Google Business Profile
Search your business on Google while logged into your Google account. If you are not logged into the correct user account associated with your business you will not be able to edit your business listing.
If logged in correctly you will see a header that says
Your Business on Google
Click on the 3 dots to the right.
Select the option Business Profile Settings
Enter the email address and select Owner or Manager for Access
Users have the option to accept the invite immediately and become active users. The page owners will get an email showing acceptance of the invite.
To learn more click here.