The Feeds module to import data is not usable without Feeds Tamper. This module ensures, for example, that the data from your import file fits into a multiple field. You can then separate the terms with a comma in one column and the Feeds Tamper will then read this comma as for each new item.
The CSV file must have the machine names of the fields in the first row. Also look at het example the module provides. References (images) ust have a file ID to reference to. One can find this ID by making a view of the files.