how to create a thumbnail via CSV import

Hi,
I’m using “advanced custom field” image field which creates a thumbnail everytime I upload an image. Here is what I’m trying to achieve.

I would like to import hundreds post via CSV import. However, i’m not sure how to import those images into my posts via CSV.
My image column in CSV file is like “http://www.abc.com/image/1.jpg”.
Is there a way to grab the image from a URL and create a thumbnail in my local directory and store that thumbnail URL later can be retrieved?

If not possible from a URL address, what about from a local directory that contains the image path? How to automate thumbnail creation and store the path and file name to the post?

Thanks very much,