Set-up and management of all your shipping rates is available under store setup > tax & shipping settings, and step-by-step instructions are provided here.

Local Shipping
Within the shipping settings, ensure you have your country of business added as a Shipping Zone and the rates are configured.

Global / Cross-border Shipping
Under shipping settings, add shipping zones for all the countries where you ship your products. If you are global, you can select country as "Rest of World".

Step-by-step instructions to set-up shipping rates