Littlebrook Air Park (3B4) is in Eliot, Maine, about 5 miles northeast of Pease International Tradeport (PSM), in Portsmouth, New Hampshire.
Take I-95 north into Maine. About a mile or so after the big bridge that crosses the river between Maine and New Hampshire, you will see signs for 236. Take 236 west towards Eliot.
After a couple of miles, you will come to a stoplight on 236, with a shopping center on the left. Take a right at the stoplight. Go about a mile or so. You should see a sign on the left for Littlebrook Airpark (it may just say Airport). Take this left. When you come to the airport, bear left around the FBO building and park in the lot on the north side.
If you like, download this 112k map of the area and print it out.
Ask at the FBO; someone there should be able to show you the airplane.