Karlie here from the Shopify Guru Team! Great question! To add a shipping method to your storefront, you would need to add in shipping rates and zones to your Shopify Admin. There are a few different ways to offer shipping rates that you can enable from your Admin.
The first step you will want to take is to add in Shipping Zones to your Shopify Admin. You can do this by following along to our step by step guide, here.
Next, you will want to add in shipping rates to go along with your newly created Shipping Zones. You can offer shipping rates depending on the price range that the customer spends, a flat rate amount or even by weight-based shipping rates. Be sure to follow our guide on price-based shipping rates and weight-based shipping rates to view how to add manual shipping rates to your storefront.
Another option for you would be to add Carrier Calculated Shipping to your storefront as well. Carrier Calculated Shipping would allow you to use a carrier, like USPS, DHL Express, UPS, or Canada Post to ship your products for you. Check out our handy help guide to walk you through the steps you need to take to set up Shopify Shipping and Carrier Calculated Shipping.
Once you've added in your Shipping Zones and your rates then you customers will be able to select a shipping method from your Shopify Checkout.
I hope this has answered your question. If not, or if you have any further questions please let me know. I will be happy to help!