How do I create a child theme for FrameMarket

I want to use FrameMarket grid style with products enlarging on hover but need to completely change the look of the pages. I tried Grid Market but this doesn't seem to do what I want.
I wish to set up my own child theme and have done this before for other WP sites. Normally I would create the child theme directory and place css style sheet in it with necessary header and import the main theme style sheet to it but can't see how to do this with FrameMarket.
Have examined GridMarket style sheet and this has a number where I would normally put the import request and am not sure what to do. Can you help please.