Hyde here from Shopify. Great question!
There are a few options for adding Carrier Calculated Shipping to your account:
If you know you'll be sticking with Shopify, I think the best option to add the Carrier Calculated Shipping feature is to check out the annual, biennial, or triennial billing options. We can add CCS for free with these, and they would save your friend between 10-25% on their Shopify subscription too!
Your friend can view the annual, biennial, and triennial billing options in their admin by heading to Settings > Plan and permissions > Compare plans > Change your billing period.
I hope that helps, let me know if you have any other questions!
All the best, Hyde.