The first question is, in which direction is it going now. If it is going forward then move the lever to the side, secure it and it will stay going forward. The lever is“L” shaped and functions as an on/off switch for the e-unit which it is attached to the e-unit with a rivet If it is not moving now, it is in neutral. Put the engine on powered track, or attach wire to the pickup roller and a ground, and add a small amount of power to it. Now move the lever from side to side putting slight forward pressure on it so that it will engage the contact on the e-unit. The engine should start to move, forward or reverse. If it is the direction you want, then move the lever to the other side and secure it. Otherwise it may bounce around and accidently make contact and engage the e-unit. If it is going in reverse keep moving the lever to cycle the engine through neutral to forward. You do not need to take the engine apart to do this.