The easiest way to do this is to first export a small set of records from
Outlook to Excel. Then open the worksheet and pay close attention to the
first row. These are the default field names Outlook uses. If you use the
exact names as the header row for the columns you wish to import, Outlook
will import your Excel data to the desired fields.
You can also manually create a field import map if you have used other names
for the columns in your worksheet. Either case depends on using field names
in the first row of your worksheet.