I started looking in to it last week and am still looking for streamlining processes.

Here's what I've been doing:

:: Export from Rithum

:: Select & Export a sample Product from within Shopify Admin (left side: Home, Orders, Products > Export Product

:: Paste the Rithum info into the relevant Fields (there are many that will be cast aside)

:: or Rename the Rithum CSV Fields to match and delete the rest

Fyi: Shopify will find any images hosted on CloudFare.

Hope that's helps.

Please let me know if you've discovered any better methods.

Thanks and good luck

Jim