In general terms, the Morrison Park is located in residential neighborhood near Steven's Square, Medford, close to the intersection where Rte 28 (Fellsway) and Rte 60 (Salem St.) meet.
The park is off of Central Ave., between Spring St. and the Fellsway, south of Salem St.
There should be parking available around the park (no residential permits to worry about).
To get to Salem St./Route 60, take Exit 32 off I-93, and head east toward Malden. Take a right at Stevens Square/Spring St, about a mile away. Head south to Central Ave (the next stop light) and take a left. The park will be one block away, on your left. (If you reach the Fellsway while driving east on Salem St., you can simply take a right onto the Fellsway/ Route 28, head south, and take a right at the light at Central Ave. The park is a couple of blocks away, on your right.)
Other notable routes:
From Somerville (east) and Cambridge: The McGrath Hwy in Somerville is Route 28; it turns into the Fellsway as it crosses the Mystic River into Medford.
From Somerville (Davis Sq.): College Av. turns into Warner, which turns into Harvard Av. as you head into Medford past Tufts. The road then becomes Mystic Valley Pkwy (at I-93), which leads to the Fellsway/Route 28 at Wellington Circle.
From Route 2 at Alewife: Take Route 16 to the left heading east (north) to I-93 northbound and exit at Exit 32—Salem St.
Take the Orange line or the MBTA local bus.
The buses that serve the area are 100 and 101, which leave hourly from Wellington (at the half hour) and Malden Ctr (at the hour), respectively. (The 101 is the bus the runs between Sullivan Sq. to Medford Sq. and then to Malden Station and back.) In Medford, it runs along Salem St; simply get off at the Stevens Square stop (near FoodMaster grocery store). The 100 runs up the Fellsway; get off at the Central Av./Medford St stop, near an auto repair shop.
If you'd rather walk from the T (or you missed the bus), the Malden Center (Orange Line) Station is about a 20-min walk to the park. Simply walk west along Pleasant St, to the Fellsway and head south to Central Av.