Hello Rachel,
Are these headers fields of those products you want to import? If so, you can create them based on 
SKUDepartmentID property of 
SKUInfo object which is created in the following part of the code:
// Get product data
string[] productData = line.Trim().Split(',');
// Create product (SKU)
SKUInfo sku = new SKUInfo();
sku.SKUName = productData[0];
sku.SKUDescription = productData[1];
sku.SKUPrice = ValidationHelper.GetDouble(productData[2], 0);
sku.SKUEnabled = true;
sku.SKUSiteID = siteId;
sku.SKUProductType = SKUProductTypeEnum.Product;
                        
DepartmentInfo department = DepartmentInfoProvider.GetDepartmentInfo(productData[3], siteName);
if (department != null)
{
  // Assign product to its department
  sku.SKUDepartmentID = department.DepartmentID;
}
Best regards,
Filip Ligac