Take the 400 and exit at Finch Ave. Exit east on Finch and get over to the left hand side as Norfinch will be the first left. Turn left (North) onto Norfinch and the park should be just up on the right under the power lines.
Take the Yonge subway line up to the Finch station. Get on any 36 bus Westbound EXCEPT 36C, which stops short at Jane. Take any other 36 bus and get off at Norfinch. It's a short walk up Norfinch to the fields.