1. Login to Google with the account the Google Business Listing Is Owned By/Created.
2: Goto : https://plus.google.com/dashboard
3: Click The Blue Manage this page Button
4: Once The Page Loads, click the gear ion from the drop down click settings.
5: Depending on the size of your Screen or Window Click Managers.
(if you don’t see settings click More and from the drop down click Managers.)
6: Click The Blue Add Manager Button.
7: When the Overlay comes up type in The Google Mail Address You want to add as a manager and then click the blue Invite button
(Ownership or Manager Both Require an active verified Google Account )
If you do not have ownership a Existing Listing You Can Have Google Call You And Verify Your Are The Business Owner By an Email on the Domain Name Listed On t the Business Listing Or Via Phone Call To The Businesses Number.
Contact Google Support:
https://support.google.com/business/contact/business_c2c_na?rd=1