Hi,
The key item to select on the one-page lister is in the Shippping Tools section (use Maximze to view the selections). There is a subsection with "Ship to Locations:". Check the Worldwide box.
Next - Below that, look for "International:" subsection and select your appropriate Shipping Method, i.e. in US select Flat or Calculated for method to use for International.
Next - Below that, look for "International Shipping Services" subsection and use the "[+]Add International Shipping Service" to add your shippers and methods, e.g. USPS Priority Mail International". Make sure you also check the "This carrier will ship to the following locations:" appropriate to shipper and method, e.g. select "Worldwide".
I am aware that some odd combinations will prevent an International rate from showing. Normally, it's using "Insurance" in combination with a service and rate that eBay doesn't recognize as a valid combination, e.g. USPS 1st Class International and Required Insurance. eBay's view: USPS doesn't Insure 1st Class International, so it's incorrect and won't display. The way to work around that specific problem is to use "Included with Shipping" selection for insurance to bundle the cost and include it as Packaging ahd Handling on the International, so it doesn't conflict as an itemized cost.
Also, run the "Error Check" when completed to see if there are any problems before you submit.
Danno