From Seattle, Bellevue, or Issaquah, follow I-90 East.
Take exit 20 (High Point Way).
At the end of the off-ramp, turn right and immediately right again.
Park along the side of this road.
Check in will be near the road junction adjacent to the off-ramp.
Here is a link to a map, with the event check-in location at the center of the map.