The directions on the website use Route 9 which now has a long detour due to the washout in September, so its probably better to stay on Route 196 until the road is rebuilt.  Here's some directions using Route 196:  The starting point for the directions is Topsham Toyota (Route 196/201 interesection):

Follow Route 196 for 17.1 miles (this will take you into Lewiston).

Turn Left onto Cedar ST/Route 196.  Follow for 0.4 miles (this will take you across the river into Auburn).

Cedar Street becomes Broad Street.  Follow for 0.3 miles.

Turn Left onto 5th Street.  Follow for 0.4 miles.

Turn Right onto Mary Carroll Street.

The game is at the Walton School, 92 Mary Carroll Street.