For Salesforce editions with API Access, administrators can use Data Loader to import Person Accounts.

Set Accounts as Person or Business Accounts via record type in your import file:

1. Add a RecordTypeId column in your import file

2. Populate it with the value of the desired Person Account record type's Id.
 

The record type Id for person accounts can be found in the setup section's URL. Access the Setup Menu:
 

Lightning: Open Object Management and type 'Person Account' in the Quick Find search to open the object by clicking into LABEL and select 'Record Types' in the menu on the left to click the desired record type's label.

Classic: Type 'Person Accounts' in the Quick Find setup search and click 'Record Types' under the Person Accounts setup tree to then click the desired record type's label.

The corresponding URLs should look something like the examples below where 012o00000008ets is the record type Id:
 

Lightning: https://<YourInstanceOrMyDomainHere>.lightning.force.com/lightning/setup/ObjectManager/PersonAccount/RecordTypes/012o00000008ets/view

Classic: https://<YourInstanceOrMyDomainHere>.salesforce.com/setup/ui/recordtypefields.jsp?id=012o00000008ets&type=PersonAccount&setupid=PersonAccountRecords

For a list of additional fields you can include when specifying an Account as a Person Account via a Person Account record type, reference the 'IsPersonAccount Fields' section of Account | SOAP API Developer Guide documentation.

Attached you will find the file, PersonAccountImportTemplate.csv containing column headers labeled to match and automatically map to standard person account fields in Salesforce. Row 2 contains example data for illustration purposes and row 3 contains notes which can be expanded to show relevant details.

Once you have prepared your file, perform an Insert via Data Loader to import your person accounts. See Insert, Update, or Delete Data Using Data Loader for more details.

Note: You can map First name and Last name Or Name (Full Name) but not both and must choose one or the other or the insert operation will fail. Should you decide to use First Name and Last Name for the import, only Last Name is required.