Link to export: Make excel-fil and import
Select the the Company Module
Select the tab Import / Export
Click on "Import/ update Companies. Review Exporting data to MS-Excel to better understand how to prepare an excel file from dRofus that could be used in this process.
...
9. Enter the letter to the coloum in your excelfil that you would like to import
Read more about excel-import
10. Select import