From Helsinki City:

Take Itäväylä out of town and stay on it past the Herttoniemi exit. 

As you pass Herttoniemi, move to the outside lane (left lane) and stay on this road as it leaves Itäväylä.

Stay on this road - Viikintie - through one set of lights, down the hill, across a set of tram tracks, 
through another set of lights, and turn right at the first set of lights which has a right filter lane - 
you will have passed The Brook on your right, about 200m before these lights. 

You are now on Tilanhoitajankaari; drive approximately 400m, past the Alepa on your right and the Kupla 
on your left, and the entrance to The Brook is on your right - it should be signposted on match days.