We'll be starting next to the Spider statue, or Maman, outside the Roppongi Hills Mori Tower.
Exit from Roppongi Station (Hibiya Line) exit 4 and go up the long escalator. You will see the Spider statue (Maman) as you reach the top.
If coming from Oedo Line, use exit 3, go to the street level, turn left and walk for a few minutes. Eventually you will come upon some concrete stairs (before the traffic light) which ascend in the direction of the largest building in the area (the blue/grey Roppongi Hills building). You will find the spider statue shortly after ascending the stairs.