Take I-5 to exit 169 (just north of the Ship Canal bridge). Follow signs for NE 45 St. At the traffic light at the end of the ramp, turn east (if you were on northbound I-5, turn right; if you were on southbound I-5, turn left).
Continue eastward on NE 45 St for just under half a mile. At 15 Ave NE (one block past University Way), turn right.
Continue south on 15 Ave NE for three blocks. At NE 41 St, turn left into the UW Central Parking Garage. Pay for parking at the gate (see rates here); tell them you which building you are going to. Park in the designated area of the garage and leave your permit on the dash.