Before enabling In-Cart Delivery Options for Shopify, make sure you meet the following requirements.
You must be on a Shopify Advanced plan or higher.
Alternatively, you can also gain access by switching your Shopify plan monthly payment to an annual payment. Or you may request access to Shopify's third-party calculated shipping rates that Shopify charges an additional fee for.
After you register for Real-Time Calculated Shipping, there may be a delay from 30 minutes to 24 hours before the ShipStation rates appear in Shopify.
In the Manage Rates pop-up, select the checkbox next to Standard Delivery in the Edit Rate pop-up, press the Done button, and click Save.
Then you can continue setting up In-Cart Delivery Options within ShipStation.