Once in Boston, go to North Station. You can get there using the MBTA Subway (the T) on either the Orange or Green Line. From Logan Airport take the Blue Line and change at State onto the Orange Line to North Station.
From North Station you can use the MBTA Commuter Rail to get to Beverly. Get on the Newburyport/Rockport Line. Prides Crossing is about 1.5 mile down the same road as the campus and the closest station stop. The train stops there several times each day, Monday through Friday. From there you can take a taxi to the campus. Beverly Farms is about 1.9 miles from the campus and is the next closest station stop. The train stops at Beverly Farms much more frequently and also on Saturday and Sunday. You can find the schedule on the MBTA Commuter Rail web site.