Step 1: Log in to your Google Merchant account:
Step 2: From legacy interface, choose the ‘Settings’ icon on the header menu. Then click on Account access
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OR
From New Interface, choose the ‘Settings’ icon on the header menu. Then click on People and access
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Step 3: Click ‘+ Add user’ email:
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Step 4: Toggle the Admin access, then click on Add user to finish
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