One useful collection of primary source material for the Greek and Roman time period is:
Loeb Classical Library, in PA3000-6700, on the third floor.
The green set is for Greek writings and the red set is for Roman writings, Search a historian or poet or philosopher as an author in the library catalog for exact call numbers.
Other ideas for primary sources include:
Of course, for written documents a reliable translation can be used since you are not expected to read any ancient language.
Listed here are examples of document collections in print only (no online access). One is in the Reference collection on the first floor, but like many primary source collections, the others are in the general collection.