Hi Armando,
Currently the Variant Required field.is not one of the available fields in the product import spec. Here is a link to the product import spec with a sample xls for your reference:
http://www.smith-consulting.com/Forum...
As an alternative, if you want to update all your variants as required after you import them in the cart you can issue the following SQL statement in SSMS:
update smith_productvariants set variantrequired=1
We can add the Variant Required field to the import spec if you would like it should be pretty easy to program, let me know and I can provide you a quote it should only take a day to add it.
Thanks