They sit in the same places as undergrad students...technically they have a higher ticket priority so they are more likely to get AA or A seats, but C deck is usually better than AA, though A is usually not bad :)
Here is the official blurb:
Undergraduate student seat locations will be determined by class rank with rank-4 getting the best seats followed by rank-3, rank-2, rank-1, and rank-0.
Graduate student seat locations will be determined by the number of credit hours completed as a graduate student or by the highest-class rank attained as an undergraduate if that undergraduate work was done at The Ohio State University, whichever rank is larger.