To use the Small Package Quotes or LTL Freight Quotes app in Shopify, your Shopify subscription must contain a feature called Third-party calculated shipping rates.
This feature is standard on the Advanced Shopify plan. It can be added to the Basic Shopify or Shopify plan by calling Shopify customer support (888-746-7439). Adding the feature to one of these other plans will increase your monthly subscription rate by $20. Typically Shopify will agree to add the feature to your existing Shopify plan for free if you agree to annual (instead of monthly) billing.