The following page has all the information you need regarding how/when and where to apply for a U.S. passport.
It takes between 6 to 8 weeks to get your passport. Plan ahead!
and the fees are $150 (normal), $250 (expedited)
You will need a birth certificate to apply for your passport.
In case you want to practice your Spanish while at it…
If you are traveling to Spain for less than three months there is no need for a visa. If you are going to be in Spain for an entire semester you will need a student visa.
More info to come.