You are likely missing the Advanced/Business selling form.
It is longer, clearer, and explains your options better.
Scroll down to Shipping Details-> International Shipping
Choose Flat Rate or Calculated*
Choose-> Custom Location
Choose-> USA
And fill in the information required.
NOW-- do you want to ship overseas?
As a newbie, don't.
But when you are more comfortable, choose Offer An Additional Service and choose from the list.
But not yet.
*If you can ship LetterRate , go with Flat Rate. If you must either track or use Parcel Rates, choose Calculated. There is more to be said about this, but that's another question.