The two distinct sections on this window let you either search for an existing customer OR create a new customer.
Only one section can be used at a time depending on your intent.
Note:
The Create New Customer performs a search to ensure that you don't duplicate an existing customer.
If no match is found, you can proceed with the Make Sale wizard to create a new account.
The New customer window will be populated with your search information.
If one or more matches are found, work with the customer to find the correct match and proceed with the existing account.
If none of the customers found are correct, you can override the search results and create a new account if you have manager override permissions.