Going back to the top of the shipping page is Shipping Methods. There is an Add Shipping Method at the bottom of the section which brings you to a new screen. Here you can give it a name, a note and choose Automated (Instant Checkout) or Manual (Invoice). Enable it so it shows up in your store as an option.
Next is domestic or international. The price chart is one that I entered the info for the current USPS First Class Commercial rates. The Courier API one don’t use. The last time I checked these were outdated and there has been no updates if this has been fixed.
After that is if you offer insurance and how much you will charge.
Plus if you offer tracking and handling fees.
And there is more. You can set up package dimensions. At the bottom you can add a weight margin. I have 10% added to weight and dimension and .5 oz added to weight. The Instant Checkout isn’t exact and you will have to play around with these to get it right. The way that you know it isn’t right is that you have to pay more for shipping than what the buyer was charged.
It is just that simple to set up a shipping method. It isn’t really but it is important to figure out since the buyer can’t check out of your without one.