When you import contacts, you can either import a contact
- with just an Organization Name (no Title, First Name, Middle Name, Last Name or Suffix).
- with a First Name and/or Last Name (no Organization Name).
Each contact must have either an Organization Name or it must have a First/Last Name.
If you are importing into the "Is Organization" field, then this must correspond appropriately.
If you want to specify where the contact works, use the "Company Name" for this purpose.
Here's a typical import, using First Name and Last Name: