You can find campus map material on the university's website. We're in the first building at the East entrance of the university, right before the Stuhlsatzenhaus.
By air: Saarbruecken has its own airport which features direct flights to Berlin, Hamburg and Luxembourg. For all other destinations fly from/to Frankfurt (FRA) or Luxembourg. Note that Frankfurt Hahn (HHN) is fairly inconvenient, do not confuse this with Frankfurt International Airport (FRA).
By bus: Buses go very frequent from downtown to bus stop 'Universität Mensa' and cost about 2.50 EUR. Instructions see here.
By car: Use the east entry of the university. You can then park your car directly at CISPA. GPS destination: Stuhlsatzenhausweg 85, Saarbruecken (see map above).