To find books in IRIS about the relations between the United States and a specific country, use the subject heading "United States Foreign Relations" followed by the name of the country.
So if you're looking for books about America's relations with Mexico, enter
To limit your results to books owned by the Dana Library,
After you click on Search, you'll be given an alphabetical list of subject headings; the terms that best correspond to your search will be toward the top.
In this case IRIS indicates that Dana Library has about 24 books that have been assigned the subject heading united states foreign relations mexico.
Click on the subject heading link to see the records.
You will be presented with a list of authors and titles.
Select Details to see the information about a specific title.
The call number, that is, the combination of letters and numbers by which the book is filed on the shelf, is listed below the owning library's name.
Since this books is in the Stacks and is In-Library, it should be available on the second floor.