Most portlets have an Import utility, and the procedure for importing text files is the same throughout. From the appropriate portlet, right-click and select Import, browse to the location of the file, select the file, and click Import.
When importing seed files into the application you must import many of them in a specific order.
The import operation does not validate this order. If you inadvertently import files in the wrong order, then clean out your database and reseed correctly.