Creating Variation Listings using CSV Catalogue Import file

Can anyone point me to any resources that will help me learn how to create listings with Size Variations on Amazon by importing the CSV product creation spreadsheet?

I want to learn how to create listings for products which are to be sold in different sizes.

I don't want to do it one at a time, so creating products using CSV upload is preferable.

A step-by-step video would be great but a written guide would be better than nothing!