Step 1 - Go to Your Google Business profile - https://business.google.com/
Step 2 - Clicks on three dots
Step 3 - Click on Google Business Profile Settings
Step 4 - Click on People and Access
Step 5 - Click on the user you want to give the primary owner access
Step 6 - Select primary owner and hit save
Note - If a user has been added recently, you can add someone as a primary owner only after 7 days