The accelerators are three green rollers behind the Multi-Barrel Gun pocket on the left side of the lower playing area. When they are moving they can accelerate the ball upwards into either the funnel pop bumpers or the accelerator target area to complete the accelerator mission. The best way to accomplish that mission is to hit the ball above the left triangular bumper and just under the Multi-Barrel Gun pocket. The best way to do this is let the ball run down the right flipper, activating the flipper as the ball gets close to the end.
To get the rollers moving the ball must pass by the rollers three times. Yellow indicator lights will light up indicating the number of times this has happened. The rollers will continue moving for two minutes, after which they will stop and the indicator lights will start to go out. To get them moving again, knock the ball past the rollers again.