To access the store as one of the administrators, you need to be an administrator user with root access (equals the role "Administrator") or an Administrator user with any custom role, including the Manage administrators permissions.
NOTE: You cannot use this feature to access a root administrator account.
To use the feature:
Locate the administrator profile you require in the user list and click the email address to open the account details.
From the Profile actions drop-down box, choose the action Log in as this admin:
The Admin area, accessible to the selected admin user, will open in a new browser tab. Your current user session will be terminated, and you will be logged in to the store as the user you selected.
To quit operating as this user, sign out.