We need a bit more information to answer this question.
- Is the position paid or unpaid?
- Does the position require special skills? (looking for a computer programmer, for example)
- Is it possible to work throughout the year, or just the summer?
- Could this lead to a full time job?
Even with that information, a lot depends on the specific University or College you are recruiting from. At a small college you may be able to locate a specific professor who teaches something your potential intern needs to know. He or she may be able to directly recommend someone, or post an ad for you in class, or in a specific student area.
A large University may have a formal policy. You might have to work with their HR department to list an opening.
But you need to formalize exactly what you are looking for and what you offer before contacting the school.